Procalcitonin and proinflammatory cytokine clearance during continuous venovenous haemofiltration in septic patients

How to use biomarkers of infection or sepsis at the bedside: guide to clinicians

Sepsis is defined as a life-threatening organ dysfunction caused by a dysregulated host response to infection. In this context, biomarkers could be considered as indicators of either infection or dysregulated host response or response to treatment and/or aid clinicians to prognosticate patient risk. More than 250 biomarkers have been identified and evaluated over the last few decades, but no biomarker accurately differentiates between sepsis and sepsis-like syndrome. Published data support the use of biomarkers for pathogen identification, clinical diagnosis, and optimization of antibiotic treatment. In this narrative review, we highlight how clinicians could improve the use of pathogen-specific and of the most used host-response biomarkers, procalcitonin and C-reactive protein, to improve the clinical care of patients with sepsis. Biomarker kinetics are more useful than single values in predicting sepsis, when making the diagnosis and assessing the response to antibiotic therapy. Finally, integrated biomarker-guided algorithms may hold promise to improve both the diagnosis and prognosis of sepsis. Herein, we provide current data on the clinical utility of pathogen-specific and host-response biomarkers, offer guidance on how to optimize their use, and propose the needs for future research.

Comparison of the Clinical Effectiveness of AN69-oXiris versus AN69-ST Filter in Septic Patients: A Single-Centre Study

INTRODUCTION

The clinical effectiveness of AN69-oXiris remains unclear. This study aimed to compare the effects of AN69-oXiris and AN69-ST filters on cytokine levels and clinical improvement in septic patients.

METHODS

This prospective observational study recruited septic patients who underwent blood purification in the First Affiliated Hospital of Soochow University between December 2019 and May 2020. Patients were assigned to an AN69-oXiris (oXiris) or AN69-ST (ST) group based on their preferred filter. Patients' clinical data, cytokine levels, and prognostic indicators were analysed at baseline (T0), 24 h after treatment (T1), and at the end of the treatment (T2).

RESULTS

Forty-four patients participated in this study (22 patients in each group). Participants in both groups showed improvements in mean arterial pressure (MAP) values, oxygenation indices, and urinary output, and decreased vasoactive-inotropic scores (VISs), heart rates, lactic acid levels, and serum creatinine levels after blood purification. Reductions in cytokine levels were observed at T1 in both groups. Improvement the haemodynamic status was higher in the oXiris group than in the ST group at T2 (MAP: 79.0 [76.0, 85.0] vs. 77.0 [72.75, 79.25] mm Hg, p = 0.04; VISs: 9.10 [0.00, 16.69] vs. 19.05 [10.60, 26.33], p = 0.03, respectively). Patients in the oXiris group also had lower cytokine levels than those in the ST group at T1 (tumour necrosis factor-α: 24.55 [16.9, 30.15] vs. 30.15 [23.38, 34.13] pg/mL, p = 0.04; interleukin (IL)-6: 66.63 [46.21, 102.20] vs. 125.48 [79.73, 167.97] pg/mL, p = 0.01; IL-8: 53.59 [35.10, 66.01] vs. 63.60 [45.58, 83.37] pg/mL, p = 0.04; IL-10: 13.50 [10.35, 18.68] vs. 17.15 [13.80, 21.95] pg/mL, p = 0.04, respectively). There were no significant differences between the 2 groups regarding hospital mortality, intensive care unit length of stay (LOS), and hospital LOS.

CONCLUSION

Blood purification using the AN69-oXiris or AN69-ST filter proved useful for septic patients, which was associated with reduced cytokine levels and improved clinical condition. Patients treated with AN69-oXiris had a more remarkable improvement in haemodynamic status and lower cytokine levels than those treated with AN69-ST filter, but there were no differences in clinical outcomes. Further investigations are needed to prove this finding.

Kinetics of serum procalcitonin in patients with acute mesenteric ischemia and bowel infarction after cardiac surgery

BACKGROUND

The present study reports perioperative changes in PCT levels occuring in cardiac patients with acute mesenteric ischemia (AMI) undergoing laparotomy. The aim of this study was to demonstrate that PCT kinetics may confirm the presence of AMI after cardiac surgery, distinguishing between bowel infarction and diffuse ischemia.

METHODS

PCT values from adult patients undergoing laparotomy for AMI after elective or urgent cardiac surgery (January 2010 - December 2019) were determinated at the ICU admission after cardiac surgery, 24 hours later and at the onset of clinical symptoms. Patients affected by diffuse intestinal ischemia with no need for bowel resection were allocated to Group A (n.8), patients presented with intestinal necrosis requiring small or large bowel resection were allocated to Group B (n.12).

RESULTS

At the beginning of the abdominal symptoms, PCT levels increased in both group, compared to those immediately after cardiac surgery. The PCT increasing resulted much more evident in patients presenting with intestinal necrosis - Group B (20.65 ng/ml [IQR8.47-34.5] vs. 4.31 ng/ml [IQR 8.47-34.5], p <0.05), rather than in those with diffuse ischemia - Group A (13.25 ng/ml [IQR 5.97-27.65] vs. 10.4 ng/ml [IQR 3.68-14.05], p 0.260). This trend was confirmed in the subgroup of patients undergoing CVVHD and in patients who experience AMI recurrence.

CONCLUSIONS

Increasing PCT values after cardiac surgery are proportional to the severity of wall ischemia and high levels of PCT are predictive of intestinal necrosis. Routine PCT monitoring after cardiac surgery should be considered extremely useful in suggesting the possibility of abdominal complications, alerting medical staff to the need of prompt treatment.

Procalcitonin in special patient populations: Guidance for antimicrobial therapy

PURPOSE

Procalcitonin (PCT) is an endogenous hormone that increases reliably in response to bacterial infection, and measurement of serum PCT levels is recommended to help guide antimicrobial therapy. The utility of PCT assessment in special patient populations (eg, patients with renal dysfunction, cardiac compromise, or immunocompromised states and those undergoing acute care surgery) is less clear. The evidence for PCT-guided antimicrobial therapy in special populations is reviewed.

SUMMARY

In the presence of bacterial infection, nonneuroendocrine PCT is produced in response to bacterial toxins and inflammatory cytokines, resulting in markedly elevated levels of serum PCT. Cytokine induction in nonbacterial inflammatory processes activated by acute care surgery may alter the interpretation of PCT levels. The reliability of PCT assessment has also been questioned in patients with renal dysfunction, cardiac compromise, or immunosuppression. In many special populations, serum PCT may be elevated at baseline and increase further in the presence of infection; thus, higher thresholds for diagnosing infection or de-escalating therapy should be considered, although the optimal threshold to use in a specific population is unclear. Procalcitonin-guided antimicrobial therapy may be recommended in certain clinical situations.

CONCLUSION

Procalcitonin may be a reliable marker of infection even in special populations with baseline elevations in serum PCT. However, due to unclear threshold values and the limited inclusion of special populations in relevant clinical trials, PCT levels should be considered along with clinical criteria, and antibiotics should never be initiated or withheld based on PCT values alone. Procalcitonin measurement may have a role in guiding de-escalation of antibiotic therapy in special populations; however, the clinician should be aware of disease states and concomitant therapies that may affect interpretation of results.

Do we need new trials of procalcitonin-guided antibiotic therapy?

Using biomarkers as a guide to tailor the duration of antibiotic treatment in respiratory infections is an attractive hypothesis assessed in several studies. Recent work aiming to summarize the evidence assessed the effect of a procalcitonin (PCT)-guided antibiotic treatment on outcomes in acute lower respiratory tract infections (LRTI), suggesting that significant reductions in antibiotic duration occur when using a PCT-guided algorithm. However, controversial evidence also suggested PCT-guided algorithms were associated with increased antibiotic duration and increased incidence of Clostridium difficile, without any impact on mortality, in real-world settings. So, although using PCT-guided antibiotic stewardship is promising, after more than a decade of randomized controlled trials on this topic the evidence in its favor is still less than compelling due to limitations in trial design, not taking into consideration fundamental aspects of PCT biology, and the absence of evidence-based antimicrobial duration in intervention and control groups. In this commentary we highlight some questions and limitations of primary PCT study data that might impact interpretation and clinical use of PCT at the bedside.

The influence of hemodialysis membrane permeability on serum procalcitonin values in patients on maintenance hemodialysis

BACKGROUND

Procalcitonin (PCT) has emerged as a marker of infection and it could be useful for detection of systemic bacterial infections in patients with end-stage renal disease (ESRD) undergoing hemodialysis (HD). The aim of this study was to assess the influence of HD membrane permeability to PCT serum levels in noninfected HD patients on maintenance HD.

METHODS

In a prospective comparative study, we measured PCT serum levels and C reactive protein (CRP) before and after HD in 36 sessions (18 sessions of HD with low-flux = Group L; and 18 sessions with high flux membranes = Group H), in 18 chronic HD patients without history of infection.

RESULTS

Sessions of HD by high-flux membranes (Group H) displayed median PCT values that were significantly decreased after dialysis (0.21 ng/mL [0.13-0.41] vs. 0.18 ng/mL [0.10-0.24], p <0.001) but median PCT significantly increased after HD sessions by low-flux membranes (Group L) (0.21 ng/mL [0.14-0.33] vs. 0.25 ng/mL [0.14-0.36]; p = 0.008). CRP values were significantly increased after HD in both groups. CRP correlated with PCT values only in group H before HD (r = 0.49; p = 0.36).

CONCLUSIONS

PCT represents a useful diagnostic marker for systemic bacterial infection. However, there is a need for specific reference ranges to be developed in patients with renal failure undergoing HD; also, PCT serum levels must be interpreted according to the HD membrane permeability.

Patterns of C-reactive protein ratio predicts outcomes in healthcare-associated pneumonia in critically ill patients with cancer

PURPOSE

Describe the patterns of C-reactive protein relative changes in response to antibiotic therapy in critically ill cancer patients with healthcare-associated pneumonia (HCAP) and its ability to predict outcome.

METHODS

Secondary analysis of a prospective cohort of critically ill cancer patients with HCAP. CRP was sampled every other day from D0 to D6 of antibiotic therapy. Patients were classified according to an individual pattern of CRP-ratio response: fast - CRP at D4 of therapy was <0.4 of D0 CRP; slow - a continuous but slow decrease of CRP; non - CRP remained ≥0.8 of D0 CRP; biphasic - initial CRP decrease to levels <0.8 of the D0 CRP followed by a secondary rise ≥0.8.

RESULTS

129 patients were included and septic shock was present in 74% and invasive mechanical ventilation was used in 73%. Intensive care unit (ICU) and hospital mortality rates were 47% and 64%, respectively. By D4, both CRP and CRP-ratio of survivors were significantly lower than in nonsurvivors (p<0.001 and p=0.004, respectively). Both time-dependent analysis of CRP-ratio of the four previously defined patterns (p<0.001) as ICU mortality were consistently different [fast 12.9%, slow 43.2%, biphasic 66.7% and non 71.8% (p<0.001)].

CONCLUSION

CRP-ratio was useful in the early prediction of poor outcomes in cancer patients with HCAP.

Biomarkers kinetics in the assessment of ventilator-associated pneumonia response to antibiotics - results from the BioVAP study

PURPOSE

Our aim was to evaluate the role of biomarker kinetics in the assessment of ventilator-associated pneumonia (VAP) response to antibiotics.

MATERIALS AND METHODS

We performed a prospective, multicenter, observational study to evaluate in 37 microbiologically documented VAP, the kinetics of C-reactive protein (CRP), procalcitonin (PCT), mid-region fragment of pro-adrenomedullin (MR-proADM). The kinetics of each variable, from day 1 to 6 of therapy, was assessed with a time dependent analysis comparing survivors and non-survivors.

RESULTS

During the study period kinetics of CRP as well as its relative changes, CRP-ratio, was significantly different between survivors and non-survivors (p=0.026 and p=0.005, respectively). On day 4 of antibiotic therapy, CRP of survivors was 47% of the initial value while it was 96% in non-survivors. The kinetics of other studied variables did not distinguish between survivors and non-survivors. In survivors the bacterial load also decreased markedly. Adequate initial antibiotic therapy was associated with lower mortality (p=0.025) and faster CRP decrease (p=0.029).

CONCLUSIONS

C-reactive protein kinetics can be used to identify VAP patients with poor outcome as soon as four days after the initiation of treatment. (Trial registration - NCT02078999; registered 3 August 2012).

Prognostic value of procalcitonin in hospitalized patients with lower respiratory tract infections

Lower respiratory tract infections are common and potentially lethal conditions and are a major cause of inadequate antibiotic prescriptions. Characterization of disease severity and prognostic prediction in affected patients can aid disease management and can increase accuracy in determining the need for and place of hospitalization. The inclusion of biomarkers, particularly procalcitonin, in the decision taken process is a promising strategy. This study aims to present a narrative review of the potential applications and limitations of procalcitonin as a prognostic marker in hospitalized patients with lower respiratory tract infections. The studies on this topic are heterogeneous with respect to procalcitonin measurement techniques, cutoff values, clinical settings, and disease severity. The results show that procalcitonin delivers moderate performance for prognostic prediction in patients with lower respiratory tract infections; its predictive performance was not higher than that of classical methods, and knowledge of procalcitonin levels is most useful when interpreted together with other clinical and laboratory results. Overall, repeated measurement of the procalcitonin levels during the first days of treatment provides more prognostic information than a single measurement; however, information on the cost-effectiveness of this procedure in intensive care patients is lacking. The results of studies that evaluated the prognostic value of initial procalcitonin levels in patients with community-acquired pneumonia are more consistent and have greater potential for practical application; in this case, low procalcitonin levels identify those patients with a low risk of adverse outcomes.

Personalized treatment of severe pneumonia in cancer patients

Patients with cancer are at increased risk for sepsis as a consequence of immunosuppression. The hospital mortality remains elevated and it could be attributed to antibiotic failure because of the presence of multiresistant pathogens. Once the patient is critically ill, the use of the American Thoracic Society/Infectious Diseases Society of America classification does not seem very useful in the assessment of outcomes and the choice of antimicrobials. In critically ill patients, the characteristics of clinical response to antibiotics are usually inaccurate and occur late in the course of disease. So, the sequential evaluation of C-reactive protein-ratio is useful in the early identification of patients with antibiotic failure. To achieve safe and efficient antimicrobial therapy, we proposed an algorithm that may aid clinicians in their decision-making process.

Effects of the volume of processed plasma on the outcome, arterial pressure and blood procalcitonin levels in patients with severe sepsis and septic shock treated with coupled plasma filtration and adsorption

AIMS

To understand how coupled plasma filtration and adsorption (CPFA) could influence the time course of the advanced stages of sepsis, mean arterial pressure (MAP) and norepinephrine dosage.

METHODS

Patients with severe sepsis and septic shock with ≥2 organ failures not responding to volume resuscitation and vasopressor infusion were treated with CPFA within 8 h of admission to the intensive care unit.

RESULTS

Thirty-nine patients were treated (median age: 63 years, median SAPS II score: 45) and 28 survived advanced sepsis. In the latter, the median MAP increased and the norepinephrine dosage decreased significantly after CPFA, whereas in the nonsurvivors these values did not change significantly. The volume of treated plasma was significantly higher in survivors than nonsurvivors.

CONCLUSION

These results suggest a possible existence of a dose-response effect for CPFA. Future studies are therefore recommended to evaluate the efficacy of this treatment and to determine its best timing and intensity.

Procalcitonin in the recognition of complications in critically ill surgical patients

BACKGROUND

Procalcitonin (PCT) is a relatively new, promising indirect parameter for infection. In the intensive care unit (ICU) it can be used as a marker for sepsis. However, in the ICU there is a need for reliable markers for clinical deterioration in the critically ill patients. This study determines the clinical value of PCT concentrations in recognizing surgical complications in a heterogeneous group of general surgical patients in the ICU.

MATERIAL AND METHODS

We prospectively collected PCT concentration data from April 2010 to June 2012 for all general surgical patients admitted to the ICU. Both the relationships between PCT levels and events (diagnostic and therapeutic interventions) as well as between PCT levels and surgical complications (abscesses, bleeding, perforation, ischemia, and ileus) were studied.

RESULTS

PCT concentrations were lower in patients who developed complications than those who did not develop complications on the same day, although not significant (P = 0.27). A 10% increase in PCT levels resulted in a 2% higher complication odds, but again this was not significant (odds ratio [OR], 1.020; 95% confidence interval [CI], 0.961-1.083; P = 0.51). Even a 20% or 30% increase in PCT concentrations did not result in higher complication probability (OR, 1.039; 95% CI, 0.927-1.165 and OR, 1.057; 95% CI, 0.897-1.246). Furthermore, an increase in PCT levels did not show an increase or a reduction in the number of diagnostic and therapeutic interventions.

CONCLUSIONS

An increase in PCT levels does not help to predict surgical complications in critically ill surgical patients.

Techniques of extracorporeal cytokine removal: a systematic review of human studies

BACKGROUND AND AIMS

Hypercytokinemia is believed to be harmful and reducing cytokine levels is considered beneficial. Extracorporeal blood purification (EBP) techniques have been studied for the purpose of cytokine reduction. We aimed to study the efficacy of various EBP techniques for cytokine removal as defined by technical measures.

METHOD

We conducted a systematic search for human clinical trials which focused on technical measures of cytokine removal by EBP techniques. We identified 41 articles and analyzed cytokine removal according to clearance (CL), sieving coefficient (SC), ultrafiltrate (UF) concentration and percentage removed.

RESULTS

We identified the following techniques for cytokine removal: standard hemofiltration, high volume hemofiltration (HVHF), high cut-off (HCO) hemofiltration, plasma filtration techniques, and adsorption techniques, ultrafiltration (UF) techniques relating to cardiopulmonary bypass (CPB), extracorporeal liver support systems and hybrid techniques including combined plasma filtration adsorption. Standard filtration techniques and UF techniques during CPB were generally poor at removing cytokines (median CL for interleukin 6 [IL-6]: 1.09 mL/min, TNF-alpha 0.74 mL/min). High cut-off techniques consistently offered moderate cytokine removal (median CL for IL-6: 26.5 mL/min, interleukin 1 receptor antagonist [IL-1RA]: 40.2 mL/min). Plasma filtration and extracorporeal liver support appear promising but data are few. Only one paper studied combined plasma filtration and adsorption and found low rates of removal. The clinical significance of the cytokine removal achieved with more efficacious techniques is unknown.

CONCLUSION

Human clinical trials indicate that high cut-off hemofiltration techniques, and perhaps plasma filtration and extracorporeal liver support techniques are likely more efficient in removing cytokines than standard techniques.

Diagnostic value of serum procalcitonin in patients with chronic renal insufficiency: a systematic review and meta-analysis

BACKGROUND

The diagnostic value of procalcitonin (PCT) for patients with renal impairment is unclear.

METHODS

We searched multiple databases for studies published through December 2011 that evaluated the diagnostic performance of PCT among patients with renal impairment and suspected systemic bacterial infection. We summarized test performance characteristics with the use of forest plots, hierarchical summary receiver operating characteristic (HSROC) curves, and bivariate random effects models.

RESULTS

Our search identified 201 citations, of which seven diagnostic studies evaluated 803 patients and 255 bacterial infection episodes. HSROC-bivariate pooled sensitivity estimates were 73% [95% confidence interval (95% CI) 54-86%] for PCT tests and 78% (95% CI 52-92%) for CRP tests. Pooled specificity estimates were higher for both PCT and CRP tests [PCT, 88% (95% CI 79-93%); CRP, 84% (95% CI, 52-96%)]. The positive likelihood ratio for PCT [likelihood (LR)+ 6.02, 95% CI 3.16-11.47] was sufficiently high to be qualified as a rule-in diagnostic tool, while the negative likelihood ratio was not low enough to be used as a rule-out diagnostic tool (LR- 0.31, 95% CI 0.17-0.57). There was no consistent evidence that PCT was more accurate than CRP test for the diagnosis of systemic infection among patients with renal impairment.

CONCLUSIONS

Both PCT and CRP tests have poor sensitivity but acceptable specificity in diagnosing bacterial infection among patients with renal impairment. Given the poor negative likelihood ratio, its role as a rule-out test is questionable.

Biomarker-guided antibiotic therapy in adult critically ill patients: a critical review

Biomarkers of infection, namely C-reactive protein and procalcitonin (PCT), are potentially useful in the diagnosis of infection as well as in the assessment of its response to antibiotic therapy. C-reactive protein variations overtime appears to have a good performance for the diagnosis of infection. Procalcitonin shows a better correlation with clinical severity. In addition, to overcome the worldwide problem of antibiotic overuse as well as misuse, biomarker guidance of antibiotic stewardship represents a promising new approach. In several randomized, controlled trials, including adult critically ill patients, PCT guidance was repeatedly associated with a decrease in the duration of antibiotic therapy. However, these trials present several limitations, namely high rate of patients' exclusion, high rate of algorithm overruling, long duration of antibiotic therapy in the control group, disregard the effect of renal failure on PCT level, and above all a possible higher mortality and higher late organ failure in the PCT arm. In addition, some infections (e.g., endocarditis) as well as frequent nosocomial bacteria (e.g., Pseudomonas aeruginosa) are not suitable to be assessed by PCT algorithms. Therefore, the true value of PCT-guided algorithm of antibiotic stewardship in assisting the clinical decision-making process at the bedside remains uncertain. Future studies should take into account the issues identified in the present review.

Prognostic categorization of intensive care septic patients

Sepsis is one of the leading worldwide causes of morbidity and mortality in critically-ill patients. Prediction of outcome in patients with sepsis requires repeated clinical interpretation of the patients’ conditions, clinical assessment of tissue hypoxia and the use of severity scoring systems, because the prognostic categorization accuracy of severity scoring indices alone, is relatively poor. Generally, such categorization depends on the severity of the septic state, ranging from systemic inflammatory response to septic shock. Now, there is no gold standard for the clinical assessment of tissue hypoxia which can be achieved by both global and regional oxygen extractabilities, added to prognostic pro-inflammatory mediators. Because the technology used to identify the genetic make-up of the human being is rapidly advancing, the structure of 30 000 genes which make-up the human DNA bank is now known. This would allow easy prognostic categorization of critically-ill patients including those suffering from sepsis. The present review spots lights on the main severity scoring systems used for outcome prediction in septic patients. For morbidity prediction, it discusses the Multiple Organ Dysfunction score, the sequential organ failure assessment score, and the logistic organ dysfunction score. For mortality/survival prediction, it discusses the Acute Physiology and Chronic Health Evaluation scores, the Therapeutic Intervention Scoring System, the Simplified acute physiology score and the Mortality Probability Models. An ideal severity scoring system for prognostic categorization of patients with systemic sepsis is far from being reached. Scoring systems should be used with repeated clinical interpretation of the patients’ conditions, and the assessment of tissue hypoxia in order to attain satisfactory discriminative performance and calibration power.

In vitro evaluation of high mobility group box 1 protein removal with various membranes for continuous hemofiltration

The high mobility group box 1 protein (HMGB1) is an alarmin that plays an important role in sepsis and has been recognized as a promising target with a wide therapeutic window; however, no drugs and devices are currently in practical use. We hypothesized that hemofilters composed of porous membranes or cytokine-adsorbing membranes could remove HMGB1 from the blood. We performed experimental hemofiltration in vitro using four types of hemofilters composed of different membranes specifically designed for continuous hemofiltration. The test solution was a 1000-mL substitution fluid containing 100 µg of HMGB1 and 35 g of bovine serum albumin. Experimental hemofiltration was conducted for 360 min in a closed loop circulation system. Among the four membranes, surface-treated polyacrylonitrile (AN69ST) showed the highest capacity to adsorb HMGB1; it adsorbed nearly 100 µg of HMGB1 in the initial 60 min and showed a markedly high clearance rate (60.8 ± 5.0 mL/min) at 15 min. The polymethylmethacrylate membrane had half of the adsorption capacity of the AN69ST membrane. Although the highest sieving coefficient for HMGB1 was obtained with the high cut-off polyarylethersulfone membrane, which correlated with a constant filtrate clearance rate, albumin loss was observed. However, no such removal of both HMGB1 and albumin was observed with the polysulfone membrane and tubing. We conclude that continuous hemofiltration using the AN69ST membrane is a promising approach for HMGB1-related sepsis.

Intermittent versus continuous renal replacement therapy: a matter of controversy

BACKGROUND

Acute Renal Failure (ARF) requiring some form of replacement therapy is a frequent complication in the critically ill patient. Despite potential therapeutic advantages the expectation of an improvement in patient outcomes using Continuous Renal Replacement Therapy (CRRT) compared to conventional Intermittent Haemodialysis (IHD) remains controversial.

AIMS AND METHOD

This article will review the literature on the issues surrounding the use of IHD versus CRRT in the management of the critically ill patient. Articles were selected according to level of evidence with priority given to meta-analyses and randomised controlled trials.

DISCUSSION

Several operational features of CRRT allow this technique to be tolerated more easily in critical illness than IHD. The gradual removal of fluid reduces the incidence of hypotension and the risk of volume overload. Decreased variability in the concentration of solutes enables greater azotemia control. However, CRRT is required to operate uninterrupted to achieve a treatment dose that is equivalent to a conventional IHD treatment schedule. In the absence of definitive evidence to validate superior patient survival and return of renal function there is disagreement as to the most appropriate form of Renal Replacement Therapy (RRT) for the critically ill patient. The introduction of 'hybrid' therapies offers a further alternative treatment strategy, which combine favourable aspects of IHD and CRRT.

CONCLUSION

The decision to use IHD or CRRT should be guided by the therapeutic needs of the patient rather than the operational differences between the two techniques. The resources and expertise available at the organisation are also important in determining the mode best able to manage the critically ill patient at any stage and may change according to the severity of illness. The emergence of hybrid therapies provides a compromise option which encompasses many of the features of both systems, but does not embrace all options of either approach.

Continuous arteriovenous hemodialysis and continuous venovenous hemofiltration in burn patients with acute renal failure

Acute renal failure (ARF) is a very common condition that may occur in patients with major burn injuries. The majority of burn patients with ARF have a high mortality rate, ranging from 73% to 100%. There are several ways to treat ARF in burn patients, including peritoneal dialysis (PD), intermittent hemodialysis, and continuous renal replacement therapy (CRRT). CRRT is generally used in patients in whom intermittent hemodialysis has failed to control hypovolemia, as well as in patients who cannot tolerate intermittent hemodialysis. Additionally, PD is not suitable for patients with burns within the abdominal area. For these reasons, most patients with unstable hemodynamic conditions receive CRRT. In this study (conducted in our burn unit between 1997 and 2004), six burn patients received CRRT: three received continuous arteriovenous hemodialysis (CAVHD) and the other three received continuous venovenous hemofiltration (CVVH). The patients were all males, with a mean age of 49.8 years (range, 27-80 years), and a mean burnt surface area of 65.1% (range, 30-95%). Four patients died due to multiple organ failure, and two patients recovered from severe ARF. CRRT has been proven safe and useful for burn patients with ARF. According to this study, we conclude that CVVH is an appropriate tool for treating ARF, with a lower incidence of vascular complications than CAVHD.

Identification of proteins in slow continuous ultrafiltrate by reversed-phase chromatography and proteomics

Continuous modes of renal replacement therapy (CRRT) are increasingly being utilized in the intensive care unit. The removal of cytokines and other inflammatory proteins during ultrafiltration may be responsible for some of the beneficial effects of CRRT. We used proteomic tools to identify proteins found in the ultrafiltrate from a patient with acute renal failure. Identification of these proteins could help elucidate the mechanism(s) of improved outcome with continuous renal replacement therapy. Protein was loaded on a reversed-phase C4 column and eluted with stepwise isocratic flows starting with 0%, 5%, 10%, 25%, and 50% of acetonitrile. Effluent was collected, pooled, desalted, and separated by two-dimensional gel electrophoresis (2DE). Reversed-phase separation improved the resolution and the number of spots seen on the gels. Protein spots were digested with trypsin and spotted onto MALDI plates. Proteins were identified by either peptide mass fingerprinting using a MALDI-TOF mass spectrometer or by peptide sequencing using a MALDI-TOF/TOF tandem mass spectrometer. From 196 spots cut, 47 were identified, representing multiple charge forms of 10 different proteins. Proteins identified were albumin, apolipoprotein A-IV, beta-2-microglobulin, lithostathine, mannose-binding lectin associated serine protease 2 associated protein, plasma retinol-binding protein, transferrin, transthyretin, vitamin D-binding protein and Zn alpha-2 glycoprotein. Continuous renal replacement therapy is frequently used in acutely ill patients with renal failure. Removal of proteins occurs during this process. The physiological significance of this protein removal is unclear. Identification of these proteins will lead to better understanding of the role of protein removal in continuous renal replacement therapy.

Renal replacement therapy with high-cutoff hemofilters: Impact of convection and diffusion on cytokine clearances and protein status

BACKGROUND

High-cutoff hemofilters are characterized by an increased effective pore size designed to facilitate the elimination of inflammatory mediators in sepsis. This study compares diffusive versus convective high-cutoff renal replacement therapy (RRT) in terms of cytokine clearance rates and effects on plasma protein levels.

METHODS

Twenty-four patients with sepsis-induced acute renal failure were studied. A polyflux hemofilter with a cutoff point of approximately 60 kd was used for RRT. Patients were randomly allocated to either continuous venovenous hemofiltration (CVVH) with an ultrafiltration rate of 1 L/h (group 1) or 2.5 L/h (group 2) or continuous venovenous hemodialysis (CVVHD) with a dialysate flow rate of 1 L/h (group 3) or 2.5 L/h (group 4). Interleukin-1 (IL-1) receptor antagonist (IL-1ra), IL-1beta, IL-6, tumor necrosis factor-alpha (TNF-alpha), and plasma proteins were measured daily.

RESULTS

CVVH achieved significantly greater IL-1ra clearance compared with CVVHD (P = 0.0003). No difference was found for IL-6 (P = 0.935). Increasing ultrafiltration volume or dialysate flow led to a highly significant increase in IL-1ra and IL-6 clearance rates (P < 0.00001). Peak clearances were 46 mL/min for IL-1ra and 51 mL/min for IL-6. TNF-alpha clearance was poor for both RRT modalities. A significant decline in plasma IL-1ra and IL-6 clearance was observed in patients with high baseline levels. Protein and albumin losses were greatest during the 2.5-L/h hemofiltration mode.

CONCLUSION

High-cutoff RRT is a novel strategy to clear cytokines more effectively. Convection has an advantage over diffusion in the clearance capacity of IL-1ra, but is associated with greater plasma protein losses.

Mass transfer, clearance and plasma concentration of procalcitonin during continuous venovenous hemofiltration in patients with septic shock and acute oliguric renal failure

Objectives

To measure the mass transfer and clearance of procalcitonin (PCT) in patients with septic shock during continuous venovenous hemofiltration (CVVH), and to assess the mechanisms of elimination of PCT.

Setting

The medical department of intensive care.

Design

A prospective, observational study.

Patients

Thirteen critically ill patients with septic shock and oliguric acute renal failure requiring continuous venovenous postdilution hemofiltration with a high-flux membrane (AN69 or polyamide) and a 'conventional' substitution volume (< 2.5 l/hour).

Measurements and main results

PCT was measured with the Lumitest PCT Brahms^® in the prefilter and postfilter plasma, in the ultrafiltrate at the beginning of CVVH (T0) and 15 min (T15'), 60 min (T60') and 6 hours (T6h) after setup of CVVH, and in the prefilter every 24 hours during 4 days. Mass transfer was determined and the clearance and the sieving coefficient were calculated according to the mass conservation principle. Plasma and ultrafiltrate clearances, respectively, at T15', T60' and T6h were 37 ± 8.6 ml/min (not significant) and 1.8 ± 1.7 ml/min (P < 0.01), 34.7 ± 4.1 ml/min (not significant) and 2.3 ± 1.8 ml/min (P < 0.01), and 31.5 ± 7 ml/min (not significant) and 5 ± 2.3 ml/min (P < 0.01). The sieving coefficient significantly increased from 0.07 at T15' to 0.19 at T6h, with no difference according to the nature of the membrane. PCT plasma levels were not significantly modified during the course of CCVH.

Conclusions

We conclude that PCT is removed from the plasma of patients with septic shock during CCVH. Most of the mass is eliminated by convective flow, but adsorption also contributes to elimination during the first hours of CVVH. The effect of PCT removal with a conventional CVVH substitution fluid rate (<2.5 l/hour) on PCT plasma concentration seems to be limited, and PCT remains a useful diagnostic marker in these septic patients. The impact of high-volume hemofiltration on the PCT clearance, the mass transfer and the plasma concentration should be evaluated in further studies.

Continuous veno-venous hemofiltration may improve survival from acute respiratory distress syndrome after bone marrow transplantation or chemotherapy

PURPOSE

Acute respiratory distress syndrome (ARDS) may result from immunologic activity triggered by irradiation and/or chemotherapy. Hemofiltration removes plasma water and soluble components below 25 kilodaltons. The authors hypothesized that early hemofiltration might attenuate the inflammatory component of ARDS, resulting in increased survival in immunocompromised children and young adults.

METHODS

Ten children (6 bone marrow transplantation, 3 chemotherapy, 1 lymphoma/hemophagocytosis) with ARDS (Pao2/Fio2 94 +/- 37 torr) received early continuous veno-venous hemodiafiltration as adjunctive therapy for respiratory failure, regardless of renal function. Six children had normal urine output and initial serum creatinine (range 0.1-1.2 mg/dL); four had renal insufficiency (initial creatinine 1.7-2.4 mg/dL). Hemofiltration was instituted coincident with intubation. Respiratory failure was precipitated by Enterobacter sepsis in two patients and by Aspergillus in one.

RESULTS

Hemodiafiltration was performed for 13 +/- 9 days. A high rate of clearance was achieved (52 +/- 17 mL/min/1.73 m2). Duration of mechanical ventilation was 14 +/- 9 days. Nine of the 10 children were successfully extubated; 8 survived.

CONCLUSIONS

Early hemofiltration may improve survival from ARDS following bone marrow transplantation or chemotherapy. Possible mechanisms include strict fluid balance, immunomodulation through filtration of inflammatory constituents, and immunomodulation through intensive extracellular water exchange that delivers biochemicals to organs of metabolism as well as the hemofilter.

Procalcitonin and C-reactive protein plasma concentrations in nonseptic uremic patients undergoing hemodialysis

OBJECTIVE

To assess procalcitonin (PCT) and C-reactive protein (CRP) plasma concentrations and clearance in nonseptic end-stage renal failure patients undergoing their first three hemodialysis sessions.

DESIGN AND SETTING

Prospective observational consecutive clinical study at a university hospital.

PATIENTS

The study recruited 55 end-stage renal failure patients without evidence of systemic infection undergoing the creation of an arteriovenous fistula to start hemodialysis for the first time.

INTERVENTIONS

Blood samples were collected before and after each of the first three (4-5 h) hemodialysis sessions. PCT was assayed by immunoluminometry.

MEASUREMENTS AND RESULTS

The mean plasma concentration of PCT prior to the first three hemodialysis sessions declined significantly following each session. There was no significant difference between CRP plasma concentrations before and after hemodialysis sessions.

CONCLUSIONS

The presence of an elevated PCT in plasma of not yet dialyzed uremic nonseptic patients indicates that uremia per se and not the dialysis process is the origin of such elevation. PCT levels declined with successive hemodialysis sessions. We propose that in the not yet dialyzed uremic nonseptic patients a baseline PCT level of approx. 1.5 ng/ml should be expected. Although the mean plasma CRP level was elevated, hemodialysis had no significant effect on CRP concentration, making CRP a possible useful marker of sepsis in these patients.