Does serum creatinine rise faster in rhabdomyolysis?

Genetic inhibition of FABP4 attenuated endoplasmic reticulum stress and mitochondrial dysfunction in rhabdomyolysis-induced acute kidney injury

AIMS

Rhabdomyolysis-associated acute kidney injury (AKI) is life-threatening but effective treatments is lacking. Recently, fatty acid-binding protein 4 (FABP4) has been identified as a mediator of ischemic and toxic AKI through regulating endoplasmic reticulum (ER) stress in our previous studies. However, the role of FABP4 in rhabdomyolysis-induced AKI and extended organelle dysfunctions need to be explored and validated.

MAIN METHODS

We firstly performed mRNA-seq and bioinformatic analysis to investigate the role of FABP4. The mouse model was established via injecting glycerol to FABP4 wild type (WT) and knockout (KO) mice. Blood biochemical, inflammatory and apoptotic parameters were measured and compared across groups. Representative pathways of ER stress and mitochondrial dysfunction were also detected and quantified.

KEY FINDINGS

Comparing FABP4 WT and FABP4 KO model groups, FABP4 deficiency significantly attenuated renal dysfunction, by reducing serum creatinine (165.90 ± 15.61 μmol/L vs 35.5 ± 8.33 μmol/L, p < 0.0001) and blood urea nitrogen (89.78 ± 6.82 mmol/L vs 19.75 ± 5.97 mmol/L, p < 0.0001), and alleviating tubular injury scores. Inflammatory and apoptotic responses were alleviated by FABP4 genetic inhibition. Mechanistically, glycerol injection triggered ER stress characterized by activated IRE1, PERK, and ATF6 signaling pathways, and induced mitochondrial dysfunction supported by ultrastructural damage, energy metabolic derangement, and excessive mitochondrial fission (upregulated DRP1/downregulated OPA1). These two organelle dysfunctions were effectively relieved by FABP4 deficiency.

SIGNIFICANCE

Taken together, genetic inhibition of FABP4 protected against rhabdomyolysis-induced AKI via reducing ER stress as well as mitochondrial dysfunction. FABP4 might act as a novel therapeutic target in rhabdomyolysis-induced AKI.

Exhaustive exercise decreases renal organic anion transporter 3 function

This study aimed to investigate the effects of various types of exercise on organic anion transporter 3 (Oat3) function, a major transporter that plays a role in the secretion of a variety of drugs and endogenous compounds. Male Wistar rats were randomly allocated to non-exercise, exhaustive, acute and training exercise groups. The function of Oat3 was assessed by the uptake of [3H]-estrone sulfate ([3H]-ES) into rat renal cortical slices. Acute and training exercises had no effect on [3H]-ES uptake whereas a marked reduction in [3H]-ES uptake occurred immediately after exhaustive exercise. However, the reduction in Oat3 function was gradually recovered at 6 and 24 h after the exercise session. Importantly, the impairment of Oat3 function was associated with a decrease in renal Oat3 protein expression. Our results indicate that exhaustive exercise produces a significant impact on renal organic anion transport function, which in turn could alter the plasma level of drugs and compounds in the body.

Kinetic Glomerular Filtration Rate in Routine Clinical Practice-Applications and Possibilities

When the [creatinine] is changing, the kidney function can still be tracked with a quantitative technique called kinetic glomerular filtration rate (GFR). The equation yields useful information on the severity of acute kidney injury, the clinical course of kidney and dialysis clearances, and the timing of kidney recovery. It has been validated in at least 3 independent studies, where it performed sufficiently well in intensive care unit and kidney transplant settings, and in head-to-head comparisons with biomarkers. Because it is based on a mathematical model, the kinetic GFR faces limitations depending on the accuracy of its assumptions. As the assumptions more accurately reflect the complexities of biology, some of these limitations can be overcome in a more sophisticated model. Kinetic GFR is an easy-to-use, low-cost tool that should be more widely incorporated into medical practice.

Kinetic Estimation of GFR Improves Prediction of Dialysis and Recovery after Kidney Transplantation

BACKGROUND

The early prediction of delayed graft function (DGF) would facilitate patient management after kidney transplantation.

METHODS

In a single-centre retrospective analysis, we investigated kinetic estimated GFR under non-steady-state conditions, KeGFR, in prediction of DGF. KeGFR(sCr) was calculated at 4h, 8h and 12h in 56 recipients of deceased donor kidneys from initial serum creatinine (sCr) concentrations, estimated creatinine production rate, volume of distribution, and the difference between consecutive sCr values. The utility of KeGFR(sCr) for DGF prediction was compared with, sCr, plasma cystatin C (pCysC), and KeGFR(pCysC) similarly derived from pCysC concentrations.

RESULTS

At 4h, the KeGFR(sCr) area under the receiver operator characteristic curve (AUC) for DGF prediction was 0.69 (95% CI: 0.56-0.83), while sCr was not useful (AUC 0.56, (CI: 0.41-0.72). Integrated discrimination improvement analysis showed that the KeGFR(sCr) improved a validated clinical prediction model at 4h, 8h, and 12h, increasing the AUC from 0.68 (0.52-0.83) to 0.88 (0.78-0.99) at 12h (p = 0.01). KeGFR(pCysC) also improved DGF prediction. In contrast, sCr provided no improvement at any time point.

CONCLUSIONS

Calculation of KeGFR from sCr facilitates early prediction of DGF within 4 hours of renal transplantation.

Retooling the creatinine clearance equation to estimate kinetic GFR when the plasma creatinine is changing acutely

It is often desirable to estimate the GFR (eGFR) at the bedside to assess AKI or renal recovery. Current eGFR equations estimate kidney function when the plasma creatinine is stable, but do not work if the plasma creatinine is changing rapidly. To analyze kidney function in the acute setting, a simple formula is proposed that requires only a modest number of inputs that are readily obtainable from clinical laboratory data. The so-called kinetic eGFR (KeGFR) formula is derived from the initial creatinine content, volume of distribution, creatinine production rate, and the quantitative difference between consecutive plasma creatinines over a given time. For that period, the deciphered creatinine excretion then yields the creatinine clearance rate. The additional formula variables needed are any steady-state plasma creatinine, the corresponding eGFR by an empirical formula, and the maximum increase in creatinine per day if anuric. The kinetic formula complements clinical intuition but also adds a quantitative and visual dimension to the assessment of kidney function, demonstrated by its analysis of GFRs underlying the plasma creatinine fluctuations in several scenarios of AKI or renal recovery. Deduced from first principles regarding the physiology of creatinine balance, the KeGFR formula enhances the fundamental clearance equation with the power and versatility to estimate the kidney function when the plasma creatinine is varying acutely.

False estimates of elevated creatinine

One of the most common reasons for a nephrology consult is an elevated creatinine. An elevation in the serum creatinine concentration usually reflects a reduction in the glomerular filtration rate (GFR). Given the association of elevated creatinine and risk of cardiovascular mortality, it is important to keep in mind that at times the elevation of the creatinine is not representative of a true reduction in GFR. There are various causes of factitious elevation of creatinine. They can be broadly grouped into increased production of creatinine, interference with the assay and decreased tubular secretion of creatinine.

2009 influenza A infection and acute kidney injury: incidence, risk factors, and complications

BACKGROUND

2009 influenza A has spread globally. Respiratory complications and renal failure have been the leading causes for hospitalization and critical illness. We describe the risk factors and complications of acute kidney injury (AKI) in patients with influenza A.

METHODS

Observational study of adult patients tested for influenza A. Outcome measures include AKI [AKI Network (AKIN) criteria] and mortality.

RESULTS

From August through December 2009, 17% (89/515) of hospitalized subjects were tested positive for influenza A. The incidence of AKI (AKIN(I-III)) was 42% (37/89) in subjects with influenza A; the majority (65%, 24/37) of whom were critically ill. Risk factors for AKI included obesity, chronic kidney disease (CKD), and elevated creatine kinase. Positive influenza A status was associated with lower AKI (AKIN(I-III)) risk compared to seronegative subjects (OR 0.5, CI 0.3-0.9). Mortality in patients with influenza A and AKI requiring dialysis was 50%.

CONCLUSIONS

Obesity, CKD, and elevated creatine kinase are associated with AKI in patients with influenza A. Influenza A is not independently associated with higher incidence of AKI in hospitalized patients. AKI is an independent risk factor for mortality in patients with influenza A.

Rhabdomyolysis in the intensive care unit

Rhabdomyolysis is a clinical syndrome defined by muscle breakdown and subsequent release of intracellular contents. There are many etiologies of rhabdomyolysis, classified here as congenital and acquired; compartment syndrome secondary to trauma with reperfusion injury is one common precipitating factor. Regardless of the underlying etiology, the pathophysiology follows a similar pathway via myocyte destruction and release of myoglobin into the systemic circulation. Rhabdomyolysis-induced renal failure is caused by the precipitation of myoglobin in the renal tubules which is enhanced under acidic conditions. A high index of clinical suspicion is required to promptly recognize rhabdomyolysis, especially in the unconscious patient. Presenting symptoms include tea-colored urine and muscle weakness or fatigue. The diagnosis is confirmed most reliably with the finding of elevated serum creatine kinase levels. Early, aggressive resuscitation with either normal saline or lactated Ringer's solution to maintain an adequate urine output is the most important intervention in preventing the development of acute renal failure. There is insufficient clinical evidence supporting the routine administration of diuretics and bicarbonate to protect against the development of acute renal failure.

Gluteal compartment syndrome after lumbar laminectomy

Gluteal compartment syndrome may, in its severe form, have serious consequences. It may result in severe rhabdomyolysis, and if left untreated it can result in acute renal collapse, multiorgan failure and even death. The present report concerns a patient who developed a gluteal compartment syndrome after lumbar surgery. The syndrome was complicated by acute renal failure with high concentrations of serum creatinine kinase, myoglobin, and potassium, requiring acute haemodialysis before surgical release. The operation revealed increased intracompartmental pressure with weak or absent reaction of muscles to electric stimulation. To prevent the development of gluteal compartment syndrome during operative procedures, it is important to avoid harmful pressure to the gluteal regions on the operating table. It is also important to optimise muscle circulation by adequate hydration therapy and avoidance of nephrotoxic stimuli. If gluteal compartment syndrome develops, immediate diagnosis and surgical decompression are mandatory .

False elevation of serum creatinine following skin absorption of nitromethane complicates the clinical diagnosis of rhabdomyolysis

A patient had extensive blunt trauma from a high-speed crash in which nitromethane fuel erupted from the fuel tank and soaked into his protective multilayer jumpsuit. The clinical diagnosis was complicated because the absorption of nitromethane fuel through the skin and by inhalation falsely increased the serum creatinine value when a modified Jaffe reaction was used in the laboratory. This spurious value was "unmasked" by the use of an enzymatic method to measure the serum creatinine level. A high serum creatinine value disproportionate to the level of BUN and recent skin exposure to nitromethane were the clinical indications that suggested the differentiation of massive rhabdomyolysis from spurious hypercreatinemia. This spurious value was a confounding factor in the diagnosis of crush syndrome and rhabdomyolysis.

The clinical and biochemical features of acute renal failure due to rhabdomyolysis

Rhabdomyolysis caused 28 out of 903 (3.1%) of cases of severe acute renal failure (ARF) treated at Leeds General Infirmary over a 14-year period (1980-1993). The commonest cause of rhabdomyolysis was muscle compression, usually due to drug- or alcohol-induced coma. Other causes included fits, infection, acute limb ischemia, trauma, and heat stroke. Prognosis was relatively good, with a 78.6% survival rate and recovery of renal function to normal in all survivors who were followed up. The creatinine/urea ratio was higher in ARF due to rhabdomyolysis than in an unselected group of patients with other causes of ARF but not when the comparison was with sex- and age-matched controls with ARF. This suggests that this previously described feature of rhabdomyolysis simply reflects the increased muscle mass of a younger group of patients, rather than a specific effect of muscle damage. Clinical features of muscle damage were often absent and so the possibility of rhabdomyolysis should be considered in appropriate settings if the diagnosis is to be made early enough to administer treatment that may prevent ARF and the consequences of the compartment syndrome.