Capillary refill time as part of an early warning score for rapid response team activation is an independent predictor of outcomes

BACKGROUND

Capillary refill time (CRT) is easy, quick to perform and when prolonged in critical illness, correlates with progression of organ failure and mortality. It is utilized in our hospital's early warning score (EWS) as one of 11 parameters. We sought to define CRT's value in predicting patient outcomes, compared to the remaining EWS elements.

METHODS

Five-year prospective observational study of 6480 consecutive Rapid Response Team (RRT) patients. CRT measured at the index finger was considered prolonged if time to previous-color return was >3 s. We analyzed the odds ratio of normal vs prolonged-CRT, compared to the other EWS variables, to individual and combined outcomes of mortality, cardiac arrest and higher-level of care transfer.

RESULTS

Twenty-percent (N = 1329) of RRT-patients had prolonged-CRT (vs normal-CRT), were twice as likely to die (36% vs 17.8%, p < .001), more likely to experience the combined outcome (72.1% vs 54.2%, p < .001) and had longer hospital length of stays, 15.3 (SD 0.3) vs 13.5 days (SD 0.5) (p < .001). Multivariable logistic regression for mortality ranked CRT second to hypoxia among all 11 variables evaluated (p < 001).

CONCLUSIONS

This is the first time CRT has been evaluated in RRT patients. Its measurement is easy to perform and proves useful as an assessment of adult patients at-risk for clinical decline. Its prolongation in our population was an independent predictor of mortality and the combined outcome. This study and others suggest that CRT should be considered further as a fundamental assessment of patients at-risk for clinical decline.

Transforming growth factor-beta(1) and myofibroblasts: a potential pathway towards renal scarring in human glomerular disease

BACKGROUND/AIMS

The cellular and humoral factors involved in the development and progression of renal scarring have not been fully investigated. Transforming growth factor-beta (TGF-beta(1)) is considered to be the main fibrogenic growth factor and it is implicated in the pathogenesis of renal fibrosis in experimental and clinical nephropathies. On the other hand, collagen III is an important component of the extracellular matrix. In this study we attempted to identify any possible links between TGF-beta(1) and collagen III synthesis and expression with the expression of myofibroblasts in the evolution of renal scarring in human glomerular diseases.

METHODS

We studied retrospectively 40 patients with various types of primary and secondary glomerulonephritis (GN), with either proliferative or nonproliferative pattern, with emphasis on the renal synthesis of TGF-beta(1) and collagen III (detected by in situ hybridization) and their expression (detected by immunohistochemistry) as well as myofibroblast expression. The possible links of TGF-beta(1) expression with myofibroblast distribution (alpha-smooth muscle actin, alpha-SMA(+) cells) and with conventional histopathology and renal function was also examined.

RESULTS

TGF-beta(1) protein and mRNA were detected in the renal tubular epithelial cells and interstitium and to a lesser extent within glomeruli of patients with GN. Collagen III was mainly detected in the interstitium (peritubular and periglomerular areas) and to a lesser extent in the glomeruli. Messenger RNA for collagen III followed a similar peritubular and periglomerular distribution to that of TGF-beta(1) and alpha-SMA(+) interstitial cells. The intensity of interstitial TGF-beta(1) protein expression was significantly related to the degree of interstitial fibrosis (r = 0.628, p < 0.01), tubular atrophy (r = 0.612, p < 0.01), interstitial collagen III expression (r = 0.478, p < 0.05), and serum creatinine values (r = 0.722, p < 0.001). Also there was a close positive correlation between the severity of interstitial myofibroblast expression and interstitial TGF-beta(1) (r = 0.412, p < 0.05), as well as collagen III (r = 0.409, p < 0.05). In addition, a significant correlation was found between glomerular TGF-beta(1) expression and severity of glomerulosclerosis (r = 0.620, p < 0.01).

CONCLUSION

The results of this study suggest that TGF-beta(1) plays an important role in the pathogenesis of fibrosis developing in human kidney, during the evolution of glomerular disease. Interstitial myofibroblasts may contribute to interstitial fibrosis through the synthesis and release of both TGF-beta1 and collagen III.

Myofibroblasts and the progression of crescentic glomerulonephritis

BACKGROUND

The cellular and humoral factors involved in the pathogenesis of glomerulosclerosis and renal fibrosis following a crescentic glomerulonephritis have not been fully elucidated. Myofibroblasts and transforming growth factor-beta (TGF-beta) have been implicated in the development of experimental and clinical renal fibrosis. We have attempted to identify these mediators in crescentic glomerulonephritis and determine their role in the progression of the disease.

PATIENTS AND METHODS

We studied retrospectively 21 patients with crescentic and necrotizing glomerulonephritis (CNG) with emphasis on the renal expression (detected by immunohistochemistry) of myofibroblasts (alpha-smooth muscle actin+ cells), TGF-beta and collagen (III and IV) as well as their relationship with the clinical outcome of these patients. In situ hybridization histochemistry was applied to determine the site of synthesis of TGF-beta1 and collagen III. All the patients were treated by immunosuppression and followed up for a median period of 14 months.

RESULTS

Myofibroblasts and TGF-beta were detected in the crescents as well as in the periglomerular and tubulointerstitial areas in CNG biopsies. TGF-beta1 was also detected within renal tubular cells. The percentage of glomeruli with fibrotic and fibrocellular crescents was positively correlated with the severity of Bowman's capsule disruption (r = 0.631, P < 0.01) and with the intensity of myofibroblast expression in the interstitium (r = 0.504, P < 0.05). Strong interstitial immunostain for myofibroblasts and TGF-beta was also noted in association with interstitial fibrosis. In situ hybridization revealed the site of synthesis of TGF-beta1 to be the renal tubular cells of patients with CNG. By contrast, the site of synthesis of collagen III appeared to be confined to interstitial cells surrounding vessels, tubules and the glomeruli in a distribution identical to that of myofibroblasts. There was a significant positive correlation between the number of interstitial alpha-SMA+ cells and both interstitial TGF-beta (r = 0.591, P < 0.01) and interstitial collagen IV (r = 0.588, P < 0.01). In addition, the number of interstitial alpha-SMA+ cells and the extent of immunostain for collagen IV were positively correlated with the final serum creatinine (r = 0.517, P < 0.05 and r = 0.612, P < 0.01 respectively) and partially predicted functional outcome (R2 = 26.7% and 37.5% respectively) as well as the response to treatment. An association was observed between periglomerular myofibroblasts and the generation of fibrotic and fibrocellular crescents.

CONCLUSION

These observations suggest a causal link between myofibroblasts and fibrotic crescent formation. We also believe that interstitial myofibroblasts are actively involved in the pathogenesis of interstitial fibrosis in CNG.

Pharmacologic control of angiotensin II ameliorates renal disease while reducing renal TGF-beta in experimental mesangioproliferative glomerulonephritis

We evaluated the effect of blocking angiotensin II (AngII) on the development of proteinuria and glomerular injury in antithymocyte serum (ATS) glomerulonephritis. Disease was induced in Sprague-Dawley rats by a single intravenous injection of rabbit ATS. Three groups of rats were considered: group 1 (n = 13), ATS rats with no therapy; group 2 (n = 13), ATS rats treated with angiotensin-converting enzyme inhibitor (40 mg/L lisinopril in the drinking water); and group 3 (n = 13), ATS rats treated with AngII receptor antagonist (50 mg/L L-158,809 in the drinking water). Treatment started 3 hours after ATS injection and lasted 4 days. An additional group of control rats (group 4, n = 13) received preimmune serum. At day 4, ATS rats developed proteinuria (46+/-5 mg/d v control 12+/-1 mg/d; P < 0.01), which was prevented by both lisinopril and L-158,809 (14+/-0.2 mg/d and 15+/-1.6 mg/d, respectively, P < 0.01 v ATS). Systolic blood pressure was comparable in ATS rats and in controls (119+/-4 mm Hg v 120+/-2 mm Hg). Systolic blood pressure values were significantly decreased after either lisinopril or L-158,809 (104+/-3 mm Hg and 101+/-5 mm Hg, respectively; P < 0.01 v ATS). Serum creatinine levels were similar in all groups. Quantitation of proliferating cells and macrophages by analysis of proliferating cell nuclear antigen-positive and ED1-positive cells/glomerular cross-section showed a marked increase in proliferating cell nuclear antigen-positive cells in glomeruli of ATS rats over controls (12.6+/-0.5 cells/glomerular cross-section v 1.9+/-0.2 cells/glomerular cross-section; P < 0.01), which was significantly (P < 0.01) prevented by both treatments (lisinopril, 5.7+/-1.0 cells/glomerular cross-section; L-158,809, 4.8+/-1.5 cells/glomerular cross-section). The increase in ED1-positive cells (10+/-0.7 cells/glomerular cross-section v controls, 1.8+/-0.2 cells/glomerular cross-section; P < 0.01) was also significantly (P < 0.01) reduced by lisinopril and L-158,809 (4.1+/-0.7 cells/glomerular cross-sections and 2.6+/-0.6 cells/glomerular cross-section, respectively). Blocking of AngII activity prevented almost completely the formation of microaneurysms in ATS rats (percent of glomeruli with microaneurysms: ATS, 11.5%+/-3.5%; ATS + lisinopril, 0.4%+/-0.2%; ATS + L-158,809, 0.8%+/-0.8%; controls, 0%). Because AngII is a potent inducer of renal transforming growth factor-beta (TGF-beta), a cytokine involved in the regulation of cell proliferation, matrix deposition, and monocyte migration (which is overexpressed in the kidney of ATS rats), we then evaluated the effect of AngII inhibitors on renal gene expression of TGF-beta1 and on urinary TGF-beta1. TGF-beta1 mRNA levels in kidneys of ATS rats were 3.6-fold higher than those of controls and were reduced by 46% and 32% after treatment with lisinopril and L-158,809, respectively. Urinary TGF-beta1 excretion increased in ATS (37.3+/-6.0 ng/d v controls, 13.8+/-3.4 ng/d; P< 0.01) but was normalized by lisinopril and L-158,809 (7.6+/-1.9 ng/d and 6.4+/-0.4 ng/d, respectively; P < 0.01). Thus, in ATS, blocking AngII synthesis prevents proteinuria and reduces glomerular cell proliferation and inflammatory cell infiltration, possibly by reducing excessive renal TGF-beta synthesis. These findings may be relevant for future strategies in the treatment of human mesangioproliferative glomerulonephritis.

Effect of radiographic contrast media on endothelium derived nitric oxide-dependent renal vasodilatation

The effect of diatrizoate (Urografin325) on the cumulative dose-response curve of the vasodilatory response to acetylcholine was studied in the isolated perfused rat kidney (IPRK). The effect of 1-nitroarginine methyl ester (L-NAME) (10 mumol l-1) on the cumulative concentration-response curve of the vasodilatory response to acetylcholine and sodium nitroprusside was also studied. Acetylcholine is a vasodilator dependent on nitric oxide (NO) synthesis by the endothelium; sodium nitroprusside is a vasodilator not dependent on endogenous NO synthesis and L-NAME is an inhibitor of endogenous NO synthesis. The effect of L-NAME (10 mumol l-1) on the vasodilatory effect of diatrizoate which is observed in the presence of endothelin A receptor antagonist (BQ123, 10 mumol l-1) was also studied. In all experiments an infusion of angiotensin II (5 ng min-1) was maintained to increase the vascular tone of the preparation. Acetylcholine induced vasodilatation and the maximum increase in renal perfusate flow (RPF) was 17.0 +/- 1.7%, (p < 0.05). Diatrizoate (20 mgl ml-1 perfusate concentration) which induced a sustained fall in the RPF (-31.0 +/- 1.7%, p < 0.05) had no effect on the vasodilatory response to acetylcholine, and a similar increase in the RPF (17.8 +/- 2.2%, p < 0.05) was observed. In contrast, L-NAME (10 mumol l-1) completely abolished the vasodilatory effect of acetylcholine and produced instead a modest decrease in RPF by -5.0 +/- 1.7% (p < 0.05). The vasodilatory effect of sodium nitroprusside was not affected by L-NAME, confirming its selectivity as an inhibitor of endogenous NO synthesis in the IPRK. The maximum increase in the RPF induced by sodium nitroprusside was 23.1 +/- 2.0% (p < 0.05) in the absence of L-NAME and 21.2 +/- 2.2% (p < 0.05) in its presence. L-NAME did not interfere with the vasodilatation induced by diatrizoate in the presence of BQ123. In the presence of BQ123 alone the RPF increased from 23.3 +/- 1.4 ml min-1 g-1 to 26.5 +/- 1.0 ml min-1 g-1 (p < 0.05). In the presence of L-NAME and BQ123 the RPF increased from 24.4 +/- 3.0 ml min-1 g-1 to 27.2 +/- 2.7 ml min-1 g-1 (p < 0.05). There was no difference between the two groups (p > 0.05). In conclusion, diatrizoate did not interfere with endothelium derived NO-dependent vasodilatation in the kidney. A reduced production of NO in the vascular endothelium induced by contrast media is unlikely to play any role in the pathophysiology of the increase in renal vascular resistance produced by these agents. The renal vasodilatation induced by diatrizoate is not dependent on endogenous production of NO.

Proximal tubular cell synthesis and secretion of endothelin-1 on challenge with albumin and other proteins

Abnormal traffic of proteins through the glomerular capillary has an intrinsic renal toxicity possibly linked to the subsequent process of over-reabsorption by proximal tubular cells. We investigated in vitro the effect of different protein concentrations on proximal tubular cell endothelin-1 (ET-1) synthesis. Rabbit proximal tubular RC.SV1 cell line was grown to confluence in serum-free hormonally defined medium. Cells were incubated for 6 and 24 hours with serum-free medium containing bovine serum albumin (BSA, 0.1 to 10 mg/mL). ET-1, a locally released hormone that stimulates cell proliferation and promotes extracellular matrix protein synthesis, was measured in cell supernatant by radioimmunoassay. BSA induced a significant dose-dependent increase in proximal tubular cell ET-1 synthesis. BSA and fatty acid-free BSA stimulated tubular ET-1 synthesis and release to a comparable extent, indicating that the lipid component of the molecule is not involved in the observed phenomenon. Experiments in which tubular cells grown on filters in bicameral systems were incubated with BSA (10 mg/mL) showed that ET-1 release was predominantly basolateral. The stimulatory effect on tubular ET-1 synthesis and release was not specific to albumin but was shared by immunoglobulin (Ig) G and transferrin. Exposure of proximal tubular cells for 6 and 24 hours to both proteins (1 and 10 mg/mL) resulted in a dose-dependent increase in ET-1 synthesis. These data suggest that overexposure of proximal tubular cells to proteins, as it occurs in vivo in proteinuric renal diseases, may promote excessive tubular synthesis of ET-1, which is mostly secreted toward the interstitial compartment.(ABSTRACT TRUNCATED AT 250 WORDS)

Relationship between the diuretic effect of radiocontrast media and their ability to increase renal vascular resistance

The relationship between diuresis and natriuresis induced by radiocontrast media (RCM) and their renal haemodynamic effects were investigated. The effects of the iso-osmolar iotrolan and the hyperosmolar diatrizoate on the renal vascular resistance (RVR) were studied in the filtering and non-filtering variants of the isolated perfused rat kidney (IPRK) preparation. In the non-filtering model, no tubular regulatory process can be activated. The effect of diatrizoate on the RVR of the filtering IPRK in the presence of fursemide (0.3 mmol l-1) an inhibitor of the tubuloglomerular feedback (TGF) was also investigated. There was no significant difference (p > 0.05) in the response of the filtering (n = 6) and non-filtering (n = 6) IPRK to iotrolan. The induced reduction in the renal perfusate flow (RPF) by iotrolan was 20.5 +/- 3.05% and 22.9 +/- 3.03%, respectively. The reduction in the RPF which was observed with diatrizoate in the non-filtering IPRK (n = 5, 17.5 +/- 3.04%) was significantly less (p < 0.05) in comparison to that of the filtering IPRK (n = 6, 26.9 +/- 4.28%). In the frusemide experiments, a reduction in the RPF comparable to that of the non-filtering kidney was observed (n = 5, 13.7 +/- 4.34%). This study demonstrates that the renal vascular effect of diatrizoate is partially dependent on the TGF response. No tubular regulatory mechanism was accountable for the haemodynamic effect of iotrolan. The activation of the tubular response is osmolarity dependent.

Role for endothelin in the renal responses to radiocontrast media in the rat

1. The involvement of endothelin in the renal responses to radiocontrast media was examined in the rat in vitro and in vivo using BQ123, a selective endothelin (ETA) receptor antagonist, and phosphoramidon, an endothelin-converting enzyme inhibitor. 2. For experiments in vitro, an isolated perfused rat kidney was employed perfusing in closed circuit with an albumin-based Krebs-Henseleit solution. The effects of BQ123 and phosphoramidon on the renal responses to iotrolan (iso-osmolar radiocontrast media) and diatrizoate (high-osmolar radiocontrast media) were examined. In vivo, renal conductance was measured using a Doppler flow probe in the anaesthetized rat pretreated with indomethacin, and the effects of BQ123 and phosphoramidon on the renal response to intravenous diatrizoate were examined. 3. In vitro, iotrolan and diatrizoate both produced a biphasic effect on the glomerular filtration rate, characterized by a transient increase followed by a sustained fall. Pretreatment with BQ123 (10 mumol/l), but not phosphoramidon (1 mmol/l), prevented both the increase and the sustained fall in glomerular filtration rate induced by radiocontrast media. 4. In vitro, iotrolan and diatrizoate both produced a sustained fall in renal perfusate flow. An initial increase in renal perfusate flow was only observed with diatrizoate. Pretreatment with BQ123 (10 mumol/l), but not with phosphoramidon (1 mmol/l), markedly inhibited the sustained fall in renal perfusate flow produced by both iotrolan and diatrizoate. BQ123 (10 mumol/l), however, markedly potentiated the renal vasodilatation produced by diatrizoate.(ABSTRACT TRUNCATED AT 250 WORDS)

Reduced depression of renal function by iotrolan in the isolated rat kidney

The direct effects of iotrolan, a non-ionic dimer, on renal function were compared to iopromide, a non-ionic monomer and diatrizoate, an ionic monomer using the isolated perfused rat kidney. Kidneys were perfused ex vivo at 100 mmHg in a recirculating perfusion system with an albumin-based perfusate containing angiotensin II. All contrast media were studied at starting concentration of 20 mg Iodine/ml of renal perfusate. Each contrast agent produced a biphasic effect on the glomerular filtration rate (GFR) characterised by a transient increase followed by a sustained fall. However, the sustained fall in GFR induced by iotrolan (-24.7 +/- 2.1%) was significantly smaller than that produced by diatrizoate (-40.6 +/- 3.5%, P < 0.05) but there was no significant difference in comparison to the fall induced by iopromide (-34.2 +/- 3.7%). Each contrast agent produced a sustained decrease in renal perfusate flow (RPF) with iotrolan exerting a significantly smaller response (-21.7 +/- 2.0%) than either diatrizoate (-29.4 +/- 2.6%, P < 0.05) or iopromide (-32.2 +/- 2.9%, P < 0.05). The results indicate that at an equivalent iodine concentration iotrolan produces a smaller reduction of renal function in comparison to either iopromide or diatrizoate.

Pharmacokinetics of an infusion of propofol during cardiac surgery

We have measured whole blood concentrations and pharmacokinetics of propofol administered as a constant rate infusion during cardiac surgery. Ten patients undergoing elective cardiac surgery involving cardiopulmonary bypass (seven myocardial revascularization and three aortic valve surgery) received a continuous infusion of propofol 4 mg kg-1 h-1 to supplement alfentanil analgesia. Whole blood propofol concentrations were measured by high pressure liquid chromatography. A concentration greater than 1 microgram ml-1 was achieved within 15 min of starting the infusion and remained constant throughout surgery. Volume of distribution, clearance and terminal half-life were similar to those found in non-cardiac patients.