Microproteinuria: response to operation

The glycocalyx as a permeability barrier: basic science and clinical evidence

Preclinical studies in animals and human clinical trials question whether the endothelial glycocalyx layer is a clinically important permeability barrier. Glycocalyx breakdown products in plasma mostly originate from 99.6–99.8% of the endothelial surface not involved in transendothelial passage of water and proteins. Fragment concentrations correlate poorly with in vivo imaging of glycocalyx thickness, and calculations of expected glycocalyx resistance are incompatible with measured hydraulic conductivity values. Increases in plasma breakdown products in rats did not correlate with vascular permeability. Clinically, three studies in humans show inverse correlations between glycocalyx degradation products and the capillary leakage of albumin and fluid.

Urinary albumin creatinine ratio associated with postoperative delirium in elderly patients undergoing elective non-cardiac surgery: A prospective observational study

Introduction

The blood‐brain barrier (BBB) disruption contributes to postoperative delirium, but cost‐effective and non‐invasive assessment of its permeability is not practicable in the clinical settings. Urine albumin to creatinine ratio (UACR), reflecting systemic vascular endothelial dysfunction, may be a prognostic and predictive factor associated with postoperative delirium. The aim was to analyze the relationship between UACR and postoperative delirium in elderly patients undergoing elective non‐cardiac surgery.

Materials and methods

Through stratified random sampling, a cohort of 408 individuals aged 60 years and older scheduled for elective non‐cardiac surgery were included between February and August 2019 in the single‐center, prospective, observational study. The presence of delirium was assessed using the Confusion Assessment Method (CAM) or Confusion Assessment Method for the ICU (CAM‐ICU) on the day of surgery, at 2 h after the surgery ending time and on the first 3 consecutive days with repeated twice‐daily, with at least 6‐h intervals between assessments. Urine samples were collected on one day before surgery, and 1st day and 3rd day after surgery. The primary outcome was the presence of postoperative delirium, and association of the level of UACR with postoperative delirium was evaluated with unadjusted/adjusted analyses and multivariable logistic regression.

Results

Postoperative delirium was observed in 26.75% (107 of 400) of patients within 3 days post‐surgery. UACR‐Pre (OR, 1.30; 95% CI, 1.14–1.49, p < 0.001), UACR‐POD1 (OR, 1.20; 95% CI, 1.13–1.27, p < 0.001), and UACR‐POD3 (OR, 1.14; 95% CI, 1.08–1.20, p < 0.001) between the delirium and non‐delirium groups show a significant difference, even after adjusting for age, education levels, and other factors.

Conclusion

As the marker of endothelial dysfunction, the high perioperative UACR value may be linked to the postoperative delirium in elderly patients undergoing elective non‐cardiac surgery.

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.

Proteinuria can predict prognosis after liver transplantation

Background

Proteinuria is a manifestation of renal dysfunction and it has been demonstrated to be a significant prognostic factor in various clinical situations. The study was designed to analyze prognosis of patients receiving liver transplantation as well as to determine predictive performance of perioperative proteinuria.

Methods

We retrospectively reviewed data of patients who had received a liver transplant in a medical center between 2002 and 2010. Demographic information and clinical characteristic parameters were recorded on the day of intensive care unit admission before operation and on postoperative days 1, 7, and 14.

Results

Among a total of 323 patients, in-hospital mortality and 90-day mortality rates were 13.0 % (42/323) and 14.2 % (46/323), respectively. Patients with proteinuria on admission had higher rates of acute kidney injury (26.8 % vs. 8.8 %, p < 0.001), severe infection episodes (48.8 % vs. 30.7 %, p = 0.023), hospital death (31.1 % vs. 10.1 %, p < 0.001), and 90-day mortality (37.7 % vs. 10.9 %, p < 0.001). Multivariate analysis showed that proteinuria on admission and Sequential Organ Failure Assessment (SOFA) score were independent predictors of in-hospital mortality. The discriminatory ability of proteinuria plus SOFA was even better than that of SOFA alone, especially on postoperative day 1.

Conclusions

The presence of proteinuria before liver transplantation is supposed to be recognized as a negative predictor for in-hospital survival. Moreover, the presence of proteinuria after liver transplantation can assist in the early prediction of poor short-term prognosis for patients receiving liver transplantation.

Prevention of post-traumatic clinical capillary leak syndrome

Systemic capillary leak is an early feature of the inflammatory response to localized injury, and is proportional to the severity of the inflammatory insult. Loss of local control of inflammation leads to an exaggerated systemic inflammatory response known as systemic inflammatory response syndrome (SIRS). SIRS is associated with multiple organ failure and death when there is failure to maintain homeostasis.

Whilst the application of molecular biology and recombinant techniques have produced major advances in our understanding of the mediation of the inflammatory response, there is no agent currently available which will prevent SIRS and reduce the incidence of post-traumatic multiple organ failure. In the meantime, a more practical approach to the avoidance of SIRS and its attendant capillary leak syndrome is to attempt to reduce the deleterious effects of interstitial oedema by tailoring treatment to the rapid changes in capillary permeability.

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.

Urinary kidney injury molecule 1 (KIM-1) and interleukin 18 (IL-18) as risk markers for heart failure in older adults: the Health, Aging, and Body Composition (Health ABC) Study

BACKGROUND

Kidney damage and reduced kidney function are potent risk factors for heart failure, but existing studies are limited to assessing albuminuria or estimated glomerular filtration rate (eGFR). We evaluated the associations of levels of urinary biomarkers of kidney tubular injury (interleukin 18 [IL-18] and kidney injury molecule 1 [KIM-1]) with future risk of heart failure.

STUDY DESIGN

Retrospective cohort study.

SETTING & PARTICIPANTS

2,917 participants without heart failure in the Health, Aging, and Body Composition (Health ABC) cohort.

PREDICTORS

Ratios of urine KIM-1, IL-18, and albumin to creatinine (KIM-1:Cr, IL-18:Cr, and ACR, respectively).

OUTCOMES

Incident heart failure over a median follow-up of 12 years.

RESULTS

Median values of each marker at baseline were 812 (IQR, 497-1,235)pg/mg for KIM-1:Cr, 31 (IQR, 19-56)pg/mg for IL-18:Cr, and 8 (IQR, 5-19) mg/g for ACR. 596 persons developed heart failure during follow-up. The top quartile of KIM-1:Cr was associated with risk of incident heart failure after adjustment for baseline eGFR, heart failure risk factors, and ACR (HR, 1.32; 95% CI, 1.02-1.70) in adjusted multivariate proportional hazards models. The top quartile of IL-18:Cr also was associated with heart failure in a model adjusted for risk factors and eGFR (HR, 1.35; 95% CI, 1.05-1.73), but was attenuated by adjustment for ACR (HR, 1.15; 95% CI, 0.89-1.48). The top quartile of ACR had a stronger adjusted association with heart failure (HR, 1.96; 95% CI, 1.53-2.51).

LIMITATIONS

Generalizability to other populations is uncertain.

CONCLUSIONS

Higher urine KIM-1 concentrations were associated independently with incident heart failure risk, although the associations of higher ACR were of stronger magnitude.

Loss of size selectivity of the glomerular filtration barrier in rats following laparotomy and muscle trauma

Posttraumatic microalbuminuria may be caused by either charge- or size-selective alterations in the glomerular filtration barrier, or both, and/or to a reduction in proximal tubular protein reabsorption. This study was performed to elucidate the pathophysiology of the increases in glomerular permeability occurring in rats exposed to a laparotomy or to a laparotomy and muscle trauma. In anesthetized Wistar rats (250-280 g), the left ureter was cannulated for urine collection, while simultaneously blood access was achieved. Rats were exposed to trauma by a laparotomy (L; n = 8), or by a combination of L and muscle trauma (MT; L+MT) induced by topical blunt injury of the abdominal muscles bilaterally. After L, muscles were crushed using hemostatic forceps at either 2 x 2 sites ("small" MT; n = 9), or at 2 x 5 sites ("large" MT; n = 9). Sham groups (n = 16), not exposed to a laparotomy, were used as controls. The glomerular sieving coefficients (theta) to polydisperse FITC-Ficoll-70/400 (molecular radius 13-80 A) were determined at 5 or 60 min after L and L+MT, respectively, from plasma and urine samples, and analyzed by high-performance size-exclusion chromatography. A tissue-uptake technique was used to assess theta for (125)I-labeled serum albumin. L, with or without MT, increased theta for Ficoll(55-80A) and albumin rapidly and markedly. Theta-Ficoll(70A) thus increased approximately threefold, and theta for albumin significantly, for all trauma groups. According to the "two-pore model" of glomerular permeability, these changes mainly reflect an increase in the number of large pores in the glomerular filter without any primary changes in the charge-selective properties of the filter.

Influence of low-molecular-weight hydroxyethyl starch on microvascular permeability in patients undergoing abdominal surgery: comparison with crystalloid

PURPOSE

Adequate volume therapy is essential for stable hemodynamics and sufficient urinary output perioperatively. Hydroxyethyl starch (HES) has been reported to attenuate the microvascular hyperpermeability which occasionally occurs in surgical patients. This study was carried out to evaluate the effect of low-molecular-weight HES on the urinary microalbumin/creatinine ratio (MACR), a marker of microvascular permeability, in surgical patients.

METHODS

In a prospective, controlled, and randomized clinical trial, 21 patients undergoing abdominal surgery were divided into two groups. Group HES (n = 10) received HES at 2 ml x kg(-1) x h(-1) during surgery and at 1 ml x kg(-1) x h(-1) after surgery, and additionally they received acetated Ringer's solution (AR) at a rate to keep central venous pressure (CVP) 5 mm Hg. Group AR (n = 11) received AR at a rate to keep CVP at 3-5 mmHg. MACR, soluble intercellular adhesion molecule-1 (sICAM-1), and urinary output were measured intermittently in the perioperative period.

RESULTS

MACR was significantly increased during surgery in both groups. There was no significant difference in MACR between the two groups throughout the study period. The serum concentration of sICAM-1 decreased during surgery in both groups, and that in group HES was significantly lower than that in group AR at the end of surgery. Postoperative urinary output in group HES was greater than that in group AR. The intensive care unit (ICU) stay in group HES was shorter than that in group AR.

CONCLUSION

Although low-molecular-weight HES does not improve microvascular hyperpermeability, the expansion of the intravascular volume by HES results in higher urinary output in the postoperative period than that seen with crystalloid solution. The lower concentration of sICAM-1 after surgery may be due to hemodilution.

Effects of early endotoxemia and dextran-induced anaphylaxis on the size selectivity of the glomerular filtration barrier in rats

This study was performed to investigate the glomerular permeability alterations responsible for the microalbuminuria occurring in endotoxemia and during anaphylactic shock. In anesthetized Wistar rats, the left ureter was catheterized for urine collection while, simultaneously, blood access was achieved. Endotoxemia was induced by lipopolysaccharide (LPS) from Escherichia coli, and glomerular permeability was assessed at 60 and 90 (n = 7) and 120 (n = 7) min. Anaphylaxis was induced by a bolus dose of Dextran-70, and glomerular permeability assessed at 5 min (n = 8) and 40 min (n = 9). Sham animals were followed for either 5 or 120 min. The glomerular sieving coefficients (theta) to fluorescein isothiocyanate-Ficoll (70/400) were determined from plasma and urine samples and assessed using size-exclusion chromatography (HPLC). After start of the LPS infusion (2 h), but not at 60 or 90 min, theta for Ficoll(70A) had increased markedly [from 2.91 x 10(-5) +/- 6.33 x 10(-6) to 7.78 x 10(-5) +/- 6.21 x 10(-6) (P < 0.001)]. In anaphylaxis, there was a large increase in theta for Ficolls >60 A in molecular radius already at 5 min, but the glomerular permeability was completely restored at 40 min. In conclusion, there was a transient, immediate increment of glomerular permeability in dextran-induced anaphylaxis, which was completely reversible within 40 min. By contrast, endotoxemia caused an increase in glomerular permeability that was manifest first after 2 h. In both cases, theta to large Ficoll molecules were markedly increased, reflecting an increase in the number of large pores in the glomerular filter.

Microalbuminuria in acute burn injury

Microalbuminuria is a known finding in inflammatory states. We hypothesized that urinary albumin/creatinine ratio (ACR) would correlate with injury severity and resuscitation demands after acute burns. This pilot study evaluated 30 adults admitted within 12 hours of injury with burns > or =10% total body surface area burn injury (TBSA). The urinary ACR was calculated for each patient at 7 to 12 hours, 19 to 24 hours, and 43 to 48 hours following burn injury. Microalbuminuria was defined as a urinary ACR > or =20 mg/g. Study patients (23 males, 7 females) had a mean age of 42.9 + 14.0 years and a median TBSA burn injury of 18.8%. Inhalation injury was present in 10 of the study patients, and all patients with inhalation injury had microalbuminuria at the time of admission. One study patient died. Median time from burn injury to resuscitation was 30 hours, and the median fluid requirement was 4.2 ml/kg/%TBSA. Microalbuminuria was not uniformly present in burn-injured patients during the first 48 hours after injury. ACR values early in the hospital course correlated with higher lactate concentrations early after burn injury. However, ACR correlated with neither injury severity nor resuscitation demands after burn injury during any studied time range. Microalbuminuria does not have apparent clinical utility in burn-injured patients, and other markers of injury severity and resuscitation demands should be sought.

Microalbuminuria: A marker of systemic endothelial dysfunction during burn excision

INTRODUCTION

Systemic endothelial dysfunction characterises both burn injury and surgery and can be monitored by serial immunoassay of urine albumin (microalbuminuria). The aim of this study was to assess microalbuminuria before and during burn excision and identify factors that may influence it.

METHODS

Serial half-hourly urine albumin/creatinine ratio (ACR, normal <2.3mg/mmol) was measured in 25 adult patients during 44 burn-excision procedures, at a median of 5 days post-injury. Median total body surface area (TBSA) excised was 12%.

RESULTS

Pre-operative median ACR was normal rising to 3.25mg/mmol at 1.5h of surgery (p<0.05). Per-operative ACR at 0.5, 1, 2 and 2.5h were all associated with % TBSA burn excised (p<0.04). Median intraoperative ACR at 1h was 2.3mg/mmol for surgery within 48h post-injury, 1.6 for surgery at 2-7 days and 25.5 during excisions later than 1 month after injury (p<0.05). ACR at 1h was associated with CRP at 48h post-surgery (p=0.04). Per-operative ACR was also significantly correlated with post-operative complications.

CONCLUSION

Systemic endothelial dysfunction of acute thermal injury assessed by microalbuminuria recurs with surgery, is minimal at 2-7 days post-burn and affected by % TBSA burn excised and post-operative complications.

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.

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.

The Effects of Hydroxyethyl Starch Compared with Gelofusine on Activated Endothelium and the Systemic Inflammatory Response Following Aortic Aneurysm Repair

OBJECTIVE

To investigate the effect of HES, used as a plasma volume expander, on endothelial cell activation induced by ischaemia-reperfusion in humans.

MATERIAL AND METHODS

Forty patients undergoing elective infrarenal aneurysm repair were randomised to receive either gelatine or hydroxyethyl starch solution as plasma expanders. The anaesthetic technique was standardised. All patients received the same crystalloid as per standard protocol. Urine samples and blood samples were collected at various times for assessment of microalbuminuria and von Willebrand factor (vWf) and CRP.

RESULTS

The peak C-reactive protein was significantly lower in the patients treated with HES than those treated with gelofusine [142 mg/L (113,196 mg/L) vs 246 mg/L (189,291 mg/L) mg/L, P < 0.01, Mann-Whitney test]. The peak ACR was also significantly lower in the HES treated patients (9.3 mg/mmol vs 23.3 mg/mmol, P < 0.05). The plasma level of vWf was significantly higher in the gelofusine treated patients than those treated with HES [173.5 U/dl Vs 80.5 U/dl, P < 0.001, at 4 hr; 160 U/dl Vs 82.5 U/dl, P < 0.001, at 8 hr; 191 U/dl Vs 100.5 U/dl, P < 0.001, at 12 hr; 209 U/dl Vs 81.0 U/dl, P < 0.001, at 24 hr].

CONCLUSION

HES may damp down the systemic inflammatory response and reduce endothelial cell dysfunction.

Increased glomerular permeability and pulmonary dysfunction following major surgery: correlation of microalbuminuria and PaO/FiO ratio

BACKGROUND

The aim of our trial was to evaluate the ability of microalbuminuria as an indicator of outcome and to investigate its relationship with the postoperative respiratory dysfunction in the initial postoperative period in a high-risk patient group.

METHODS

In our prospective, observational study patients were consecutively recruited following elective oesophagectomy, total gastrectomy, Whipple-resection of the pancreas and liver resection due to tumour removal. Microalbuminuria (expressed as urine albumin:creatinine ratio, M:Cr) was measured before (tp), and after surgery (t0, t6, t24, t48, t72). Multiple Organ Dysfunction Scores were monitored on ICU admission than daily (t1, t2, t3). For statistical analysis, Wilcoxon's rank-sum test, Mann-Whitney's U-test, receiver operating characteristic curve analysis and Spearman's rho test were used as appropriate.

RESULTS

One hundred and forty patients (118 survivors and 22 non-survivors) were recruited. Significantly higher Multiple Organ Dysfunction Scores were observed in non-survivors throughout the study period (P < 0.001). Microalbuminuria (Cr) increased significantly (P < 0.01) on admission to the ICU (t0) compared with the preoperative levels, but levels returned to normal within 6 h and remained so for the rest of the study. There was a significant difference between survivors and non-survivors at t0 (P < 0.01). However the ROC curve indicated that M:Cr is not a reliable descriptor of outcome. Comparison of Cr values with the PaO2/FiO2 ratio showed an inverse relationship on admission, which remained so for t24 and t48.

CONCLUSION

M:Cr measured on admission to the ICU was significantly higher in non-survivors than in survivors, and also showed an inverse relationship with the PaO2/FiO2 ratio following extended abdominal surgery. However, on admission, M:Cr did not discriminate survivors from non-survivors. Further studies are required to evaluate the prognostic value of this test for postoperative patients with risk of respiratory failure.

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.

Microalbuminuria does not reflect increased systemic capillary permeability in septic shock

OBJECTIVE

To investigate the correlation between microalbuminuria and extravascular lung water in patients in septic shock who require mechanical ventilation for severe respiratory failure.

DESIGN AND SETTING

Prospective, observational, clinical study in the 20-bed intensive care unit of a university hospital.

PATIENTS AND PARTICIPANTS

25 consecutive patients in septic shock and also in severe respiratory failure requiring mechanical ventilation.

INTERVENTIONS

Hemodynamic parameters and extravascular lung water were determined by single arterial thermodilution. Together with each hemodynamic measurement the PaO(2)/FIO(2) ratio and urinary microalbumin to creatinine ratio (M:Cr) was measured. Serum C-reactive protein (CRP) and procalcitonin (PCT) levels were also determined daily.

MEASUREMENTS AND RESULTS

The EVLW index was significantly higher than normal throughout the study. Microalbuminuria was in the normal range on entry and remained so for the rest of the study period. Serum PCT and CRP levels were significantly higher than normal at every assessment points. No significant correlation was found between M:Cr and either EVLW or PaO(2)/FIO(2).

CONCLUSIONS

In this study patients in septic shock with significantly elevated EVLW had normal urinary M:Cr, and there was no correlation between M:Cr and EWLV, and PaO(2)/FIO(2). Therefore based on the current results routine measurements of microalbuminuria to determine endothelial permeability cannot be recommended in critically ill patients.

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.

Renal tubular injury after infrarenal aortic aneurysm repair

OBJECTIVE

To investigate markers of tubular injury (glutathione-S-transferase [GST] isoforms) as early markers for renal damage in patients undergoing abdominal aortic aneurysm repair.

DESIGN

Prospective study.

SETTING

Regional teaching hospital.

PARTICIPANTS

Eight consecutive patients undergoing elective infrarenal abdominal aortic aneurysm repair.

INTERVENTIONS

All patients received a standard anesthetic technique including a dopamine infusion (3 microg/kg/min) but without supplemental renoprotective agents. Urine and blood samples were taken at induction, at 1 hour and 3 hours after limb reperfusion, and on days 1 and 2 postoperatively. Urine microalbumin and creatinine concentrations were measured using standard assays, and urine pi-GST and alpha-GST enzyme measurements were performed by a commercial immunoassay (Biotrin, Biotrin International Ltd., Co., Dublin, Ireland).

MEASUREMENTS AND MAIN RESULTS

Five patients (63%) showed a postoperative elevation of serum creatinine (median increase from baseline, 35.4%; range, 8.3% to 50.6%) that was associated with significant elevations of urinary microalbumin-to-creatinine, alpha-GST-to-creatinine, and pi-GST-to-creatinine ratios soon after clamp removal. The remaining 3 patients showed no increase in serum creatinine or urine proteins. Peak alpha-GST-to-creatinine levels were different between the 2 groups. The peak levels of GST enzymes were significantly (r(2) > 80%) associated with the percent increase in serum creatinine from baseline.

CONCLUSION

Urinary GST-to-creatinine ratios are a sensitive early biomarker for renal injury after infrarenal abdominal aortic aneurysm repair.

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.

Early post-traumatic acute respiratory distress syndrome and albumin excretion rate: a prospective evaluation of a 'point-of care' predictive test

All patients sustaining major trauma exhibit increased capillary permeability, manifested as micro-albuminuria. Urinary albumin excretion rate (AER) measured on intensive care units (ICU) can predict early post-traumatic acute respiratory distress syndrome (ARDS). This prospective study sought to evaluate AER as a practical predictive test for early ARDS. Staff at the participating centres were trained in the use of the Behring Turbitimer and the concept of AER as a predictor of early post-traumatic ARDS. AER was measured every 2 h for the first 24 h, on 54 adult blunt trauma admissions (ISS>/=18). A diagnosis of early acute lung injury (ALI) or ARDS was made using the American-European Consensus Conference criteria. Eleven patients developed ARDS, ten developed ALI, and 23 had no pulmonary dysfunction. The AER was significantly greater in those who developed ARDS 8 and 18 h after admission. The positive predictive value of the test was 64% at 8 h, the negative predictive power 73%. The test was performed most consistently in the middle 10 h of the study period. If intervention had been based on the 8 h data point result, 75% patients who had the test performed and later developed ARDS would have had intervention appropriately. In principle, testing for AER as a predictor of post-traumatic ARDS on ICU is feasible, however, this study has underlined the challenges of introducing new concepts into the ICU environment.

Differences in renal response between endovascular and open repair of abdominal aortic aneurysms

OBJECTIVES

to determine the difference in renal and systemic response between open and endovascular aneurysm repair.

MATERIALS AND METHODS

we studied prospectively 22 patients undergoing open repair (OR) and 15 patients undergoing endovascular repair (ER). Blood and urine samples were taken preoperatively (T0) and before clamping of the aorta or femoral artery (T1) and 5 min (T2), 1 h (T3), 6 h (T4), 24 h (Day 1) and 48 h (Day 2) after declamping. Albumin/creatinin ratio (AC ratio) in urine, serum albumin, serum creatinin, serum C-reactive protein and serum lactate were determined.

RESULTS

the urinary AC ratio in ER was significantly lower than in OR (p<0.001). In both groups the rise in urine albumin/creatinin ratio after declamping (T2, T3) was significant (p<0.001). C-reactive protein was raised significantly at day 1 and 2 in both groups (p<0.001) with no difference between the groups. Serum lactate values were significantly higher in OR. There was a significant increase in serum lactate 6 h after declamping in the ER group.

CONCLUSIONS

after endovascular repair renal damage is less compared to open repair. There is a significant systemic reaction to the endovascular repair causing mild, short-lasting damage to the kidney. This systemic response is most probably induced by a combination of ischaemia reperfusion injury and the surgical trauma of the procedure. Other possible explanations are discussed.

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.

Glomerular permeability and trauma: a correlation between microalbuminuria and Injury Severity Score

OBJECTIVE

To determine if there is a correlation between an increase in glomerular permeability, the magnitude of trauma, and the severity of illness.

DESIGN

Prospective study.

SETTING

Two university hospital intensive care units.

PATIENTS

Forty consecutive critically ill trauma patients admitted directly to the intensive care unit within 120 mins of their injuries.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

For each patient, urine was collected from the time of admission until 7 am the next day. Within 48 hrs, only one sample of all urine collected (5 mL) was examined for microalbuminuria and urinary creatinine. Results were expressed as the microalbuminuria/urinary creatinine ratio (MACR). The mortality rate in the intensive care unit, Injury Severity Score at the moment of admission, Acute Physiology and Chronic Health Evaluation III score, and Simplified Acute Physiology Score in the first 24 hrs were calculated for each patient. The data were analyzed using the Pearson test for linear regression and Student's t-test. During the first 24 hrs after trauma, there was an increase of MACR (6.9 +/- 0.6 mg/mmol) above normal (reference range, <3 mg/mmol) that was positively correlated with Injury Severity Score (31.4 +/- 1.9; r2 = .73, p < .05). However, there was no correlation between MACR, Acute Physiology and Chronic Health Evaluation III score, Simplified Acute Physiology Score, and mortality rate.

CONCLUSIONS

Patients with trauma show an increase in glomerular permeability during the first 24 hrs after injury. The magnitude of this increase is correlated with the extent of trauma but does not seem significant enough to be predictive of severity of illness and/or outcome.

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.

Reduced total antioxidant capacity predicts ischaemia-reperfusion injury after femorodistal bypass

BACKGROUND

Antioxidant defence systems are essential to protect the body from harmful free radicals released following ischaemia-reperfusion. The aim of this study was to examine the total antioxidant capacity (TAC) of patients with chronic critical leg ischaemia undergoing femorodistal bypass and to correlate this with lipid peroxidation, changes in capillary permeability and clinical outcome.

METHODS

Twenty-five patients, 15 men and ten women of median age 71 (range 62-79) years, and 15 matched controls were studied. Blood was taken before operation and after reperfusion, with assays performed for malondialdehyde (a product of lipid peroxidation) and total antioxidant capacity. Changes in capillary permeability were measured by changes in the urinary albumin:creatinine ratio (ACR) following reperfusion of the ischaemic leg and expressed as a percentage increase from the preoperative value. Clinical outcome in terms of the systemic inflammatory response syndrome (SIRS) was recorded.

RESULTS

Vascular patients who developed clinical evidence of a systemic inflammatory reaction following revascularization had a significantly reduced TAC compared with the controls (490 versus 860 mumol/l; P < 0.01, Mann-Whitney U test). These patients also demonstrated an increase in lipid peroxidation (0.5 versus 0.25 mumol/l, P < 0.05) and vascular permeability, as measured by the percentage increase in ACR (365 versus 130 per cent, P < 0.01).

CONCLUSION

Vascular patients with a lower TAC developed increased capillary permeability as a result of ischaemia-reperfusion, which progressed to SIRS. TAC may provide a test to identify 'at risk' patients. It may be possible to augment their defence with exogenous antioxidants.

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.

Renal impairment after hip or knee arthroplasty. Urinary excretion of protein markers studied in 59 patients

We studied renal function during and after surgery in 38 patients undergoing total hip replacement (THR) and 21 patients undergoing total knee replacement (TKR). Serum creatinine and renal excretion of albumin, IgG, protein HC and creatinine were recorded preoperatively and on days 1, 2, 4, and 8. THR patients were randomized to treatment with (n 17) or without (n 21) prophylactic isoxazolyl penicillins, which all TKR patients had. In all 3 groups, the urinary concentration of proteins increased postoperatively with a peak in the glomerular markers (albumin, IgG) on days 1 and 2, and in the tubular marker (protein HC) on days 2 and 4. There were no statistically significant differences between the groups. On day 8, all urinary protein concentrations had essentially returned to their preoperative levels. Serum creatinine decreased by 10% in THR patients on day 1 and then returned to baseline levels, but there was a gradual increase up to 13% in TKR patients.

Antioxidant depletion during aortic aneurysm repair

Ischaemia-reperfusion injury generates oxygen-derived free radicals leading to local and distant damage. A simple method of following oxidative activity is to measure the consumption of endogenous scavenging antioxidants; an enhanced chemiluminescent assay was used to study this phenomenon in 21 patients undergoing surgery for abdominal aortic aneurysm (AAA). Samples of peripheral venous blood were taken before induction of anaesthesia and then from a central venous line and the inferior mesenteric vein before, during, and after clamping of the aorta. Further specimens were taken from the central line at 2, 6 and 24 h after operation. Antioxidant concentration in the peripheral, central and inferior mesenteric blood were similar, indicating that anaesthesia and surgical dissection had no effect. Levels decreased significantly in central and inferior mesenteric blood during and after clamping, but returned to normal by 24 h. These results confirm ischaemia-reperfusion phenomena in AAA repair.

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.

Peri-operative assessment of glomerular permeability

Surgical trauma may provoke an increase in glomerular permeability. Microalbuminuria is a subclinical increase in urinary albumin ranging from 20 to 300 mg..-1. This cannot be measured with routine laboratory tests and is estimated by radioimmunoassay. It has been proposed that microalbuminuria, an expression of increased glomerular permeability, serves to reflect a generalised increase in systemic vascular permeability. In this study the degree of microalbuminuria (expressed as microalbuminuria/creatinine ratio to correct for dilutional changes) has been measured in two groups of patients undergoing either videolaparoscopic surgery (group A) or conventional, open, abdominal surgery (group B). The anaesthetic technique was standardised and the duration of surgery similar in the two groups. A significant increase (p < 0.01) in the microalbuminuria/urinary creatinine ratio occurred in patients undergoing open abdominal surgery (group B). This alteration appeared 2 h after surgery but had disappeared 24 h after the end of the operation. During surgery, there was a direct relationship between glomerular permeability and the severity of the surgical insult.

Microalbuminuria: pathogenesis, prognosis and management

The development in recent years of sensitive assays specific for albumin has facilitated extensive investigation of the pathophysiology and clinical significance of microalbuminuria. It is now clear that the appearance of microalbuminuria represents a crucial event in the natural histories of diabetes mellitus and essential hypertension. It reflects the presence of generalized vascular damage and is strongly predictive of subsequent renal failure, cardiovascular morbidity, and death. Therapeutic interventions, including strict diabetic and blood-pressure control, can reduce microalbuminuria and improve the overall prognosis. The detection and treatment of microalbuminuria in these high-risk groups should now form an integral part of their management. Large-scale screening programmes are also recommended for insulin-dependent diabetics.

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.

Claudication induces systemic capillary endothelial swelling

An in vivo model of intermittent claudication has been developed to investigate systemic reperfusion injury associated with transient muscle ischaemia. Rats were subjected to unilateral common iliac artery ligation and two weeks of intermittent hind limb muscle stimulation. Electron microscopy demonstrated a significantly increased percentage of swollen capillary endothelial cells both locally and systemically in these "claudicant" rats, compared with controls or those undergoing muscle stimulation or artery ligation alone. These results support human data suggesting that claudication induces an inflammatory response which results in systemic vascular injury.

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.

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

Serial six hourly urine collections were made for seven days on 20 patients with acute pancreatitis. Quantitative immunoassay of urinary albumin and IgG on the first urine sample after admission showed increased excretion rates in 14 and 13 patients, respectively. Urinary protein excretion rates remained normal or approached normal by seven days in 17 patients who made uneventful recoveries. The maximum urinary excretion rates of both albumin and IgG within the first 36 hours correlated with the serum C-reactive protein concentration 72 hours after admission. The highest IgG excretion rates were found in three patients who later developed severe complications. These preliminary data suggest that low proteinuria is a very early response in acute pancreatitis, and that it may reflect the severity of inflammation.