Renal insufficiency after trauma and sepsis. A prospective functional and ultrastructural analysis

Histopathological changes of organ dysfunction in sepsis

BACKGROUND

Sepsis is a highly lethal disorder. Organ dysfunction in sepsis is not defined as a clinicopathological entity but rather by changes in clinical, physiological, or biochemical parameters. Pathogenesis and specific treatment of organ dysfunction in sepsis are unknown. The study of the histopathological correlate of organ dysfunction in sepsis will help understand its pathogenesis.

METHODS

We searched in PubMed, EMBASE, and Scielo for original articles on kidney, brain, and liver dysfunction in human sepsis. A defined search strategy was designed, and pertinent articles that addressed the histopathological changes in sepsis were retrieved for review. Only studies considered relevant in the field were discussed.

RESULTS

Studies on acute kidney injury (AKI) in sepsis reveal that acute tubular necrosis is less prevalent than other changes, indicating that kidney hypoperfusion is not the predominant pathogenetic mechanism of sepsis-induced AKI. Other more predominant histopathological changes are apoptosis, interstitial inflammation, and, to a lesser extent, thrombosis. Brain pathological findings include white matter hemorrhage and hypercoagulability, microabscess formation, central pontine myelinolysis, multifocal necrotizing leukoencephalopathy, metabolic changes, ischemic changes, and apoptosis. Liver pathology in sepsis includes steatosis, cholangiolitis and intrahepatic cholestasis, periportal inflammation, and apoptosis. There is no information on physiological or biochemical biomarkers of the histopathological findings.

CONCLUSIONS

Histopathological studies may provide important information for a better understanding of the pathogenesis of organ dysfunction in sepsis and for the design of potentially effective therapies. There is a lack of clinically available biomarkers for the identification of organ dysfunction as defined by the histological analysis.

Histopathological changes in septic acute kidney injury in critically ill children: a cohort of post-mortem renal biopsies

BACKGROUND

Septic acute kidney injury (AKI) accounts for more than half of all cases of AKI in critically ill children. The renal histology was found to alter the management in more than two-third of cases of adult acute renal failure. Better insight into the pathogenesis of pediatric septic AKI could be based on developing a clearer appreciation of the histopathological changes. No comprehensive study of the histopathological features of septic AKI in critically ill children has yet been performed.

METHODS

This retrospective observational study was conducted at a level-III pediatric intensive care unit (PICU) from June 2013 to July 2014. Children (<13 years of age) who had expired due to sepsis and AKI and had post-mortem renal biopsies were included. Sepsis and AKI were defined according to the International pediatric sepsis consensus conference and Acute Kidney Injury Network (AKIN) definition and classification system, respectively.

RESULTS

A total of 708 patients were admitted to the PICU during the study period, with mortality of 24 % (n = 170) and 62 complete data of post-mortem renal biopsies were included. The median (IQR) age was 12 (4.8-36) months, pediatric risk of mortality score (PRISM) III was 14 (12-18) and the time to biopsy after death was 24 (18-26) minutes. Normal histology was the most common change 41.9 % (n = 26), followed by acute tubular necrosis (ATN) 30.6 % (n = 19). A combination of changes involving tubules, glomeruli, interstitium, and blood vessels was noted in 21 % (n = 13) of the specimens. Eight percent (n = 5) of the specimens had features consistent with thrombotic microangiopathy. Normal histology was noted in 15.4 % (n = 4/26), 50 % (n = 13/26), and 34.6 % (n = 9/26) of AKI stage-I, II, and III, respectively.

CONCLUSION

The most common renal histopathological change in septic AKI in critically ill children was normal histology followed by ATN.

Ecto-5'-nucleotidase (CD73) decreases mortality and organ injury in sepsis

The extracellular concentrations of adenosine are increased during sepsis, and adenosine receptors regulate the host's response to sepsis. In this study, we investigated the role of the adenosine-generating ectoenzyme, ecto-5'-nucleotidase (CD73), in regulating immune and organ function during sepsis. Polymicrobial sepsis was induced by subjecting CD73 knockout (KO) and wild type (WT) mice to cecal ligation and puncture. CD73 KO mice showed increased mortality in comparison with WT mice, which was associated with increased bacterial counts and elevated inflammatory cytokine and chemokine concentrations in the blood and peritoneum. CD73 deficiency promoted lung injury, as indicated by increased myeloperoxidase activity and neutrophil infiltration, and elevated pulmonary cytokine levels. CD73 KO mice had increased apoptosis in the thymus, as evidenced by increased cleavage of caspase-3 and poly(ADP-ribose) polymerase and increased activation of NF-κB. Septic CD73 KO mice had higher blood urea nitrogen levels and increased cytokine levels in the kidney, indicating increased renal dysfunction. The increased kidney injury of CD73 KO mice was associated with augmented activation of p38 MAPK and decreased phosphorylation of Akt. Pharmacological inactivation of CD73 in WT mice using α, β-methylene ADP augmented cytokine levels in the blood and peritoneal lavage fluid. These findings suggest that CD73-derived adenosine may be beneficial in sepsis.

The histopathology of septic acute kidney injury: a systematic review

Introduction

Sepsis is the most common trigger of acute kidney injury (AKI) in critically ill patients; understanding the structural changes associated with its occurrence is therefore important. Accordingly, we systematically reviewed the literature to assess current knowledge on the histopathology of septic AKI.

Methods

A systematic review of the MEDLINE, EMBASE and CINHAL databases and bibliographies of the retrieved articles was performed for all studies describing kidney histopathology in septic AKI.

Results

We found six studies reporting the histopathology of septic AKI for a total of only 184 patients. Among these patients, only 26 (22%) had features suggestive of acute tubular necrosis (ATN). We found four primate studies. In these, seven out of 19 (37%) cases showed features of ATN. We also found 13 rodent studies of septic AKI. In total, 23% showed evidence of ATN. In two additional studies performed in a dog model and a sheep model there was no evidence of ATN on histopathologic examination. Overall, when ATN was absent, studies reported a wide variety of kidney morphologic changes in septic AKI – ranging from normal (in most cases) to marked cortical tubular necrosis.

Conclusion

There are no consistent renal histopathological changes in human or experimental septic AKI. The majority of studies reported normal histology or only mild, nonspecific changes. ATN was relatively uncommon.

Effects of preoperative administration of carprofen on renal function and hemostasis in dogs undergoing surgery for fracture repair

OBJECTIVE

To evaluate effects of preoperative administration of carprofen on renal function and hemostasis in dogs undergoing general anesthesia for fracture repair.

ANIMALS

26 client-owned dogs.

PROCEDURE

Anesthesia was induced with levomethadone, diazepam, and propofol and maintained by administration of isoflurane in oxygen-nitrous oxide. Carprofen (4 mg/kg, SC) was administered 1 hour before induction to 13 dogs (group 1) and after extubation to the other 13 dogs (group 2). All dogs also received carprofen (4 mg/kg, SC, q 24 h) for the first 4 days after surgery. Renal function (glomerular filtration rate [GFR], urinary protein-to-urinary creatinine ratio [UP:UC], and results of urinalysis and biochemical analysis of plasma), hemostatic variables (bleeding time, platelet aggregation, prothrombin time [PT], activated partial thromboplastin time [APTT], and platelet count), and Hct were assessed before and at various time points after surgery.

RESULTS

Analysis of results for renal function tests, most of the hemostatic and plasma biochemical variables, and Hct did not reveal significant differences between treatment groups. Values for GFR, UP:UC, PT, APTT, and platelet aggregation were outside reference ranges in many dogs before surgery and during the first 6 hours after surgery. In most dogs, these trauma-induced pathologic changes returned to within reference ranges during the 4-day period after surgery.

CONCLUSIONS AND CLINICAL RELEVANCE

Carprofen did not cause clinically relevant adverse effects in dogs anesthetized for fracture repair after 5 days of treatment, even when it was administered before surgery or given to patients with trauma-induced alterations in renal function or hemostasis.

Detection of renal blood flow abnormalities in septic and critically ill patients using a newly designed indwelling thermodilution renal vein catheter

To evaluate alterations in renal blood flow in sepsis-induced renal failure, we developed and studied a percutaneously placed thermodilution renal blood flow catheter in eight critically ill patients. Para-aminohippurate extraction coefficients were decreased, supporting the need for renal vein sampling to determine CPAH in sepsis. Thermodilution and CPAH methods correlated strongly, confirming the reliability of this thermodilution method. Renal vascular resistance, an indicator of renal vascular function, remained unchanged throughout the bouts of sepsis. The fraction of total body arterial blood flow going to the kidneys rose significantly during recovery from sepsis. Glomerular filtration rate, which was reduced in four of seven septic patients, correlated with the fraction of total blood flow going to the kidneys. These results suggest that renal vascular abnormalities may be occurring during septic shock. Our study demonstrates that sepsis-induced renal dysfunction may occur despite normal ranges of total renal blood flow during shock.

The hourly pattern of urine solute and electrolyte excretion following standard surgical trauma

Although urine volume (and, less frequently, concentration) is often measured in the perioperative period, little attempt has been made to separate temporal phases of the intra- and postoperative response to surgery. In 7 patients undergoing standard severe single trauma and managed by a conventional regimen which included intraoperative Hartmann's solution, we have investigated the hourly pattern of urine solute and electrolyte excretion over the first 48 h. Contrary to expectation, in the first 5 h Na+ excretion increases in association with overall solute excretion, and thereafter progressively diminishes. K+ excretion increases 4 h postoperatively and remains elevated for 24 h, after which it returns to normal, even though Na+ excretion remains low. Free water excretion is negative for the first 24 h, though urine osmolality does not suggest a maximal antidiuretic response by the kidney--the highest concentration achieved being just below 800 mosmol/kg. In order to distinguish between the physiological adaptive changes due to starvation and those due to injury, the hourly pattern of urine solute and electrolyte excretion was further investigated in 12 healthy volunteers mimicking postoperative conditions. Apart from the early postoperative period, the hourly pattern of Na+, K+ and osmolar excretion shows no discernible difference from the operated group. These results show that, particularly in relation to Na+, the changes seen in the post-injury patient, even after major uncomplicated surgery, are largely adaptive, and this is especially striking at 24 h after surgery.

Patchy, intermittent ischemia in renal cortex during tourniquet shock in dog

The effect of bilateral hindlimb occlusion on the distribution of renal cortical blood flow was investigated in anesthetized dogs. Local blood flow in outer cortex (OCF) and in inner cortex (ICF) was measured by 6 platinum electrodes recording hydrogen gas clearance. Renal blood flow fell unsignificantly while hematocrit (Hct) rose from 37 to 47% during the 4 h tourniquet period. After the release of the tourniquets average arterial blood pressure fell to about 75% of control, whereas OCF and ICF were proportionately reduced towards 30--40% of control. Hct increased to 58%. Patchy, intermittent ischemia in outer and inner cortex was irregularly observed after release of the tourniquets when Hct had increased markedly, as previously found during dehydration and endotoxin shock. The sudden shifts in washouts rates from single electrodes were not accompanied by corresponding variations in total renal blood flow. Heparinization of alpha-receptor blocking did not suppress the appearance of abrupt flow changes in this period. However, sudden shifts in local flow were also seen shortly after application of the tourniquets, before Hct had increased, in this phase possibly induced by an increased renal nervous tone.

IN CONCLUSION

OCF and ICF fell to the same degree during tourniquet shock. Patchy, intermittent ischemia was observed in the renal cortex, most frequently at high Hct, but also before Hct did rise.