Acute continuous hemodiafiltration: a prospective study of 110 patients and a review of the literature

Cumulative fluid balance and mortality in elderly patients with acute kidney injury requiring continuous renal-replacement therapy: a multicenter prospective cohort study

Background

The effect of fluid balance on outcomes in elderly patients with acute kidney injury (AKI) requiring continuous renal-replacement therapy (CRRT) is not explained well. We investigated outcomes according to cumulative fluid balance (CFB) in elderly patients with AKI undergoing CRRT.

Methods

A total of 607 patients aged 65 years or older who started CRRT due to AKI were enrolled and stratified into two groups (fluid overload [FO] vs. no fluid overload [NFO]) based on the median CFB value for 72 hours before CRRT initiation. Propensity score-matching analysis was performed.

Results

The median age of included patients was 73.0 years and 60.0% of the population was male. The median 72-hour CFB value was 2,839.0 mL. The overall cumulative survival and 28-day survival rates were lower in the FO group than in the NFO group (P < 0.001 for both) and remained so after propensity score-matching. Furthermore, patients in the FO group demonstrated a higher overall mortality risk after adjustment for age, sex, systolic blood pressure, Charlson comorbidity index, Acute Physiology and Chronic Health Evaluation II score, serum albumin, creatinine, diuretic use, and mechanical ventilation status (hazard ratio, 1.38; 95% confidence interval, 1.13 to 1.89; P < 0.001). Among survivors, both the duration of CRRT and the total duration of hospitalization from CRRT initiation showed no difference between the FO and NFO groups.

Conclusion

A higher CFB value is associated with an increased risk of mortality in elderly patients with AKI requiring CRRT.

The outcome of critically ill elderly patients with severe acute renal failure treated by continuous hemodiafiltration

Objectives

To study the outcome of critically ill elderly patients with severe acute renal failure managed by continuous hemodiafiltration.

Design

Prospective study.

Setting

Intensive Care Unit of tertiary institution

Patients

Seventy-two consecutive critically ill patients of 65 years or older admitted to the ICU with severe acute renal failure. Seventy similar control patients of age < 65 years.

Intervention

Treatment of all patients with continuous hemodiafiltration. Measurements and main results: Safety and effectiveness of therapy were assessed. Main outcome measures were duration of oliguria, of ICU stay, and hospital stay for survivors, and survival to ICU discharge and to hospital discharge. Mean APACHE II score on admission was 29.8 (95% confidence interval: 28.5 to 31.1) and mean organ failure score prior to initiation of continuous hemodiafiltration was 3.9 (95% confidence interval: 3.6 to 4.2). Sepsis was present in 51 cases (70.8%) and bacteremia or fungemia in 24 (33.3%). Fifty-three (73.6%) required mechanical ventilation for > 3 days. Vasopressor drugs were used in 65 (90.2%). Continuous hemodiafiltration controlled azotemia in all patients and was only associated with minor complications. Thirty-four patients (47.2%) survived to ICU discharge and 30 (41.6%) to hospital discharge. Among survivors, duration of oliguria was 11.6 days (95% confidence interval: 9.1 to 14.1), mean duration of ICU stay 8.6 days (95% confidence interval: 6.1 to 11.) and mean duration of hospital stay 33.1 days (95% confidence interval: 28.8 to 37.4). No statistically significant difference in survival was found when these patients were compared to a control group of similar but younger patients who also received ICU care and continuous hemodiafiltration for the treatment of severe acute renal failure.

Conclusions

A greater than 40% survival was achieved in critically ill elderly patients with severe acute renal failure by the use of continuous hemodiafiltration. These patients had an in hospital survival comparable to that of younger patients. These findings support an aggressive renal replacement approach in such patients and suggest that continuous hemodiafiltration may be ideally suited to their management.

Outcome Prediction for Critically Ill Children with Acute Renal Failure Requiring Continuous Hemofiltration

Continuous hemofiltration has been used with increasing frequency for treating volume overload and acute renal failure in critically ill, hemodynamically unstable pediatric patients. This retrospective report investigates continuous hemofiltration in pediatric patients, and their survival rate. Sixty children treated between 1999 and 2001 with a diagnosis of acute renal failure and requiring continuous hemofiltration were admitted to this study to determine if pediatric risk of mortality III (PRISM III) scores were an accurate prediction of mortality. PRISM III scores were calculated on the day continuous hemofiltration commenced; mean PRISM III scores of non-survivors were significantly higher than mean scores of survivors. PRISM III scores may be a useful indicator of outcome in children receiving continuous hemofiltration.

Intradialytic nutritional support

PURPOSE OF REVIEW

Intradialytic nutritional support has been used for more than 30 years both in critically ill patients with acute renal failure and during maintenance hemodialysis. Present knowledge allows better estimation of its metabolic and nutritional efficacy, as well its effect on patient outcome.

RECENT FINDINGS

Recent data showed that intradialytic nutritional support is able to counteract these effects of dialysis on protein metabolism and to improve both nitrogen and energy balance. In maintenance hemodialysis patients, the improvement of nutritional status during nutritional support was shown to improve long-term survival. In critically ill patients with acute renal failure, protein sparing is one of the main therapeutic goals. The effect of nutritional support on patient outcome is not demonstrated. Recent data, however, showed that the improvement of nitrogen balance may be associated with a better outcome.

SUMMARY

Current information helps to better assess the effects of intradialytic nutritional support, to clarify the nutritional management of renal failure patients and to provide recommendations. Future research should focus on the possible means to improve the efficacy of nutritional support, either by modifying its components of by associating anabolic or anticatabolic agents.

Treatment of acute kidney injury: an update on the management of renal replacement therapy

PURPOSE OF REVIEW

Renal replacement therapy remains the cornerstone of management for the patient with severe acute kidney injury. Although the technology for providing renal replacement therapy has markedly advanced over the past few decades, fundamental issues regarding its management, including timing of initiation, selection of modality and dosing of therapy, remain unresolved.

RECENT FINDINGS

Although several retrospective and observational studies of the timing of initiation of renal replacement therapy have suggested improved survival with early initiation of treatment, the design of these studies does not allow definitive conclusions. Recent randomized trials have not demonstrated any benefit with regard to survival or recovery of renal function with continuous renal replacement therapy compared with intermittent hemodialysis. Increased intensity of renal support appears to be associated with improved survival; however more definitive studies are ongoing.

SUMMARY

The optimal management of renal replacement therapy in patients with acute kidney injury remains uncertain. Appropriately designed studies evaluating timing of initiation of therapy need to be undertaken. Current data suggest that modality of therapy does not impact outcome. More intensive renal support may be associated with improved outcomes; however several large randomized controlled trials assessing this question are ongoing.

Dialysis modality and dosing strategy in acute renal failure

Many fundamental aspects of the management of renal replacement therapy (RRT) in acute renal failure (ARF) remain unresolved. While data from multiple studies support the initiation of RRT, in the absence of other indications, when the BUN has reached a level of approximately 90-100 mg/dl, there are conflicting data regarding the benefit of earlier initiation of renal support. The relative efficacy of the various RRT modalities is uncertain. Despite growing utilization, a survival benefit or greater recovery of renal function has not been demonstrated for continuous renal replacement therapy (CRRT) as compared to conventional intermittent hemodialysis (IHD). Optimal dosing strategies are also poorly defined. While there is increasing evidence that more intensive renal support is associated with better outcomes in ARF, an optimal Kt/Vurea and treatment frequency for IHD remain to be established. Similarly, although data suggest that continuous venovenous hemofiltration (CVVH) should be dosed at no less than 35 ml/kg/hr (postdilution), confirmation of this dosing strategy and validation for other modalities of CRRT are required.

ESPEN Guidelines on Enteral Nutrition: Adult Renal Failure

Enteral nutrition (EN) by means of oral nutritional supplements (ONS) and tube feeding (TF) offers the possibility of increasing or ensuring nutrient intake in cases where normal food intake is inadequate. These guidelines are intended to give evidence-based recommendations for the use of ONS and TF in nephrology patients. They were developed by an interdisciplinary expert group in accordance with officially accepted standards and are based on all relevant publications since 1985. They were discussed and accepted in a consensus conference. Because of the nutritional impact of renal diseases, EN is widely used in nephrology practice. Patients with acute renal failure (ARF) and critical illness are characterized by a highly catabolic state and need depurative techniques inducing massive nutrient loss. EN by TF is the preferred route for nutritional support in these patients. EN by means of ONS is the preferred way of refeeding for depleted conservatively treated chronic renal failure patients and dialysis patients. Undernutrition is an independent factor of survival in dialysis patients. ONS was shown to improve nutritional status in this setting. An increase in survival has been recently reported when nutritional status was improved by ONS.

Acute renal failure in the ICU: assessing the utility of continuous renal replacement

Acute renal failure (ARF) in the ICU patient still remains a common problem and is associated with increased morbidity, mortality, and cost. Potential advantages of continuous renal replacement (CRRT), compared with intermittent hemodialysis (IHD) include enhanced hemodynamic stability, increased solute removal, and greater ultrafiltration. Although it was hoped that CRRT would lead to improvement in patient outcomes, there are few prospective, randomized clinical studies comparing this modality with conventional hemodialysis in the treatment of patients with ARF. The difficulties associated with designing such prospective studies are the complex status of the medical patients and the ethical dilemma of randomizing patients to a certain dialysis modality. At this time, there is no evidence to support the assertion that CRRT improves clinical outcomes compared with IHD.

Development of a continuous renal replacement program in critically ill patients

BACKGROUND

Critically ill patients encounter many obstacles, such as acute renal failure, that increases length of stay as well as hospital cost. Dialysis in these patients is often ineffective thereby prolonging the inevitable and significantly increasing the cost of care. A dialysis program that could improve patient care, potentially improve outcome and be "revenue neutral" would be ideal.

METHODS

A continuous renal replacement therapy (CRRT) program was developed to significantly impact the care of critically ill patients Using the latest CRRT equipment along with an innovative hands-on CRRT training program, a specialized CRRT team was created. Working in conjunction with the hospital business office, new revenue charge codes were created and existing codes were updated. Patients who underwent CRRT had their financial records reviewed for: hospital cost to perform CRRT, total hospital billing to the payer, CRRT revenue 881 (billing units) charged to the payer, total charges and reimbursement for the account, percentage of reimbursement, collected revenue, and payer.

RESULTS

From April 2000 to February 2002, 39 critically ill patients underwent CRRT. Initial set-up cost was US$79,622.80 and the cost of CRRT was US$222,323.98. The hospital billed for US$656,090.63 and assuming 100% reimbursement, the potential profit was US$427,678.50. However, loss of revenue, mainly from noncompliance with charge capture resulted in the hospital billing only US$386,794.32 with a total reimbursement of US$165,779.86. The 21 burn patients who underwent CRRT yielded a net profit of US$10,294.12, with the highest reimbursement from workman's compensation and private payers. The overall mortality rate was 59% and 65% for the burn patients; significantly lower than published national averages.

CONCLUSIONS

An in-house CRRT program improved patient care by providing dialysis in patients who normally would not tolerate the procedure. Although there was a loss of revenue, CRRT in the burn patients appeared "revenue neutral." Although not specifically studied in this review, based on published data, mortality rates in this population were lower than expected especially in critically ill burn patients.

A randomized clinical trial of continuous versus intermittent dialysis for acute renal failure

BACKGROUND

Acute renal failure (ARF) requiring dialysis in critically ill patients is associated with an in-hospital mortality rate of 50 to 80%. The worldwide standard for renal replacement therapy is intermittent hemodialysis (IHD). Continuous hemodialysis and hemofiltration techniques have recently emerged as alternative modalities. These two therapies have not been directly compared.

METHODS

A multicenter, randomized, controlled trial was conducted comparing two dialysis modalities (IHD vs. continuous hemodiafiltration) for the treatment of ARF in the intensive care unit (ICU). One hundred sixty-six patients were randomized. Principal outcome measures were ICU and hospital mortality, length of stay, and recovery of renal function.

RESULTS

Using intention-to-treat analysis, the overall ICU and in-hospital mortalities were 50.6 and 56.6%, respectively. Continuous therapy was associated with an increase in ICU (59.5 vs. 41.5%, P < 0.02) and in-hospital (65.5 vs. 47.6%, P < 0.02) mortality relative to intermittent dialysis. Median ICU length of stay from the time of nephrology consultation was 16.5 days, and complete recovery of renal function was observed in 34.9% of patients, with no significant group differences. Despite randomization, there were significant differences between the groups in several covariates independently associated with mortality, including gender, hepatic failure, APACHE II and III scores, and the number of failed organ systems, in each instance biased in favor of the intermittent dialysis group. Using logistic regression to adjust for the imbalances in group assignment, the odds of death associated with continuous therapy was 1.3 (95% CI, 0.6 to 2.7, P = NS). A detailed investigation of the randomization process failed to explain the marked differences in patient assignment.

CONCLUSIONS

A randomized controlled trial of alternative dialysis modalities in ARF is feasible. Despite the potential advantages of continuous techniques, this study provides no evidence of a survival benefit of continuous hemodiafiltration compared with IHD. This study did not control for other major clinical decisions or other supportive management strategies that are widely variable (for example, nutrition support, hemodynamic support, timing of initiation, and dose of dialysis) and might materially influence outcomes in ARF. Standardization of several aspects of care or extremely large sample sizes will be required to answer optimally the questions originally posed by this investigation.

Acute renal failure and dialysis in the chronically critically ill patient

Acute renal failure is a common clinical problem in the intensive care unit (ICU) and is associated with significant morbidity and mortality. There is no "magic bullet" to prevent acute renal failure or to modify the clinical course of established renal failure. The approach to therapy is directed to the early initiation of dialysis therapy. Continuous dialysis therapy is becoming the preferred form of dialysis in the ICU.

Continuous veno-venous haemodialysis with a novel bicarbonate dialysis solution: prospective cross-over comparison with a lactate buffered solution

OBJECTIVE

To compare acid-base balance, lactate concentration and haemodynamic parameters during continuous veno-venous haemodialysis (CVVHD) using bicarbonate or a lactate buffered dialysate.

METHODS

DESIGN

prospective randomized cross-over design;

SETTING

Multicentre combined adult surgical and medical intensive care units. Patients; 26 critically ill patients starting CVVHD for acute renal failure.

INTERVENTIONS

Each patient to receive 48 h of bicarbonate dialysate and 48 h of lactate dialysate with the order of the 48 h block randomized at trial entry.

RESULTS

The serum bicarbonate increased from baseline in both the lactate and bicarbonate groups over the first 48 h of treatment (16.3+/-1.53 to 22.2+/-1.41 mmol/l and 18.9+/-2.02 to 22.2+/-1.18 mmol/l, respectively) and continued to rise towards normal over the next 48 h after cross-over to the other dialysate. The H+ and pCO2 only trended higher in the lactate group. Unlike the acid base parameters, serum lactate levels varied depending on the dialysate composition. The patients initially randomized to the lactate dialysate had higher serum lactate levels and these tended to increase further after 48 h of dialysis from 2.4+/-0.8 to 2.6+/-0.4 mmol/l. However, in the following 48 h the lactate levels fell to 1.8+/-0.6 (P = 0.039) while patients were being treated with the bicarbonate dialysate. Similar results were seen in the patients initially randomized to the bicarbonate dialysate. Serum lactate remained stable over the first 48h (1.4+/-0.2 to 1.5+/-0.1 mmol/l) but after cross-over to the lactate dialysate increased to 3.1+/-0.7 mmol/l (P = 0.051). Overall, lactate levels were significantly higher during dialysis with lactate buffered solution than bicarbonate buffered solution (2.92+/-0.45 vs. 1.61+/-0.25 mmol/l P = 0.01). Mean arterial pressure trended higher during bicarbonate dialysis but did not reach statistical significance (lactate vs. bicarbonate; 71.1+/-3.1 vs. 81.3+/-5.8 mm Hg). Subgroup analysis of the patients with abnormal liver indices or increased lactate levels at initiation of dialysis (n = 15) revealed only a trend toward better bicarbonate control (lactate vs. bicarbonate; 22.00+/-1.73 vs. 22.86+/-1.09, P = 0.2). However, in this group with hepatic insufficiency elevations in serum lactate were even greater during lactate compared to the bicarbonate dialysis (3.39+/-0.68 vs. 1.78+/-0.42 P = 0.036). Patients who had elevations of lactate during lactate dialysis had a high mortality (6 of 7). These patients had an even greater disparity in lactate levels (4.3+/-1.4 vs. 1.3 +/-0.3) and blood pressure (68.0+/- 7.7 vs. 87.2+/-17.1) between lactate and bicarbonate dialysis. Due to small patient numbers these comparisons did not achieve statistical significance.

CONCLUSION

During continuous veno venous haemodialysis a bicarbonate buffered dialysis solution provided equal acid-base control but maintained more normal lactate levels than a lactate buffered dialysis solution.

Acute renal failure--which treatment modality is the best?

Despite the progress in animal research concerning the pathophysiology and the progress in clinical practice regarding the methods of therapy, the incidence and mortality of acute renal failure remain high, especially when other organs are involved. New pharmacological interventions have led to the perspective that in the near future it may be possible to prevent and/or ameliorate this devastating syndrome. Continuous dialysis therapy and the selection of a biocompatible membrane may possibly help the critically ill patient especially when parenteral nutrition and correction of electrolyte and acid-base disturbances are important. Nevertheless, more solid data are needed and one should take into consideration that acute renal failure is a multifactorial syndrome. The type of dialysis itself is not the only matter which has to be evaluated since the mortality rate can be correlated with the number of involved organs before or after the initiation of acute renal failure and with the severity of the original disease. In clinical practice, a large number of prospective studies and more sophisticated statistical methodology are needed in order to evaluate the proper treatment modality.

Epidemiology of acute renal failure and outcome of haemodiafiltration in intensive care

OBJECTIVE

To examine the epidemiology of acute renal failure (ARF) and to identify predictors of mortality in patients treated by continuous venovenous haemodiafiltration (CVVHDF).

DESIGN

Uncontrolled observational study.

SETTING

One intensive care unit (ICU) at a surgical and trauma centre.

PATIENTS

A consecutive sample of 3591 ICU treatments.

MEASUREMENTS AND RESULTS

Demographic data, indications for ICU admission, severity scores and organ system failure at the beginning of CVVHDF were set against the occurrence of ARF and ICU mortality. 154 (4.3% of ICU patients and 0.6% of the hospital population) developed ARF and were treated with CVVHDF. Higher American Society of Anaesthesiologists (ASA) status and higher Apache II score were associated with ICU incidence of ARF. However, these criteria were not able to predict outcome in ARF. A simplified predictive model was derived using multivariate logistic regression modelling. The mortality rates were 12% with one failing organ system (OSF), 38% with two OSF, 72% with three OSF, 90% with four OSF and 100% with five OSF. The adjusted odds ratio (OR) of death was 7.7 for cardiovascular failure, 6.3 for hepatic failure, 3.6 for respiratory failure, 3.0 for neurologic failure, 5.3 for massive transfusion and 3.7 for age of 60 years or more.

CONCLUSION

General measures of severity are not useful in predicting the outcome of ARF. Only the nature and number of dysfunctioning organ systems and massive transfusion at the beginning of CVVHDF and the age of the patients gave a reliable prognosis in this group of patients.

Renal replacement therapy in the ICU: the Australian experience

The structure of health care drives medical practice in a powerful way, shaping choices of therapy and approaches, and influencing scientific evidence. The Australian experience with continuous renal replacement therapy (CRRT) confirms the importance of structure. A public health system like that of Australia's contains the following variables: well-developed intensive care tradition and expertise, a dominant "closed" intensive care unit (ICU) model, well-developed training of intensive care nurses with established one-to-one nurse-patient ratios, salaried medical practitioners, overworked general dialysis units with inadequate nursing resources, and lack of fee-for-service incentive for nephrologists to see ICU patients with acute renal failure. The likely outcome of such a system is for CRRT to be run by intensive care staff. As shown by a recent regional survey, this approach, although somewhat unique, is dominant and appears to work well with excellent clinical results and constant clinical research output.

To dialyze or not to dialyze: an ethical and evidence-based approach to the patient with acute renal failure in the intensive care unit

Patients with acute renal failure in the intensive care unit have high in-hospital mortality. In this setting, decision making with regard to the initiation or discontinuation of dialysis by physicians, patients, and families is challenging because of the desire of all for the patient to recover while sparing unnecessary suffering. Decision making can be facilitated by knowledge of outcomes of the treatment of such patients in the medical literature. This knowledge assists nephrologists to distinguish those patients whose clinical situation indicates a more favorable prognosis from those whose prognosis is uncertain or definitely poor even with dialysis. This information, combined with consideration of relevant ethical guidelines, provides a framework for nephrologists to make decisions that are evidence based and ethically sound. We present and discuss two cases to show the application of evidence-based medicine and ethical considerations to decision making for patients with acute renal failure in the intensive care unit.

Acute renal failure in infants, children and adults

Acute renal failure (ARF) occurs in many critically ill patients regardless of age. A combination of events often seen in critical care settings, including shock, sepsis, hypoxia, and the use of potentially nephrotoxic medications, combine to make ARF an ongoing and important management issue in critical care medicine. Since the events leading to the development of ARF differ in infants, children, adults, and the elderly, the pathophysiology, clinical features, and treatment modalities do indeed have remarkable similarities among the different age groups.

Prognosis of patients with acute renal failure in the intensive-care unit: a tale of two eras

OBJECTIVE

To determine whether any changes occurred in the complexity of illness or survival of Mayo intensive-care unit (ICU) patients with acute renal failure (ARF) who required hemodialysis between the 1977 through 1979 period and the 1991 and 1992 era.

DESIGN

A retrospective comparison was done of 71 consecutive ICU patients with ARF during 1977 through 1979 and 71 similar consecutive patients from the 1991 and 1992 period.

MATERIAL AND METHODS

Each patient was scored for the three components of the acute physiology and chronic health evaluation (APACHE) II system (acute physiology score, age, and preexisting chronic health problems). Patient gender, postoperative status, presence of diabetes mellitus, presence of chronic renal insufficiency, and factors contributing to ARF were recorded for each patient. Patient survival and renal function at time of hospital dismissal and 12 months after initiation of hemodialysis were determined.

RESULTS

In comparison with patients in the earlier study period, those in the later study period had a signficantly improved rate of hospital survival (52% versus 32%) and 1-year survival (30% versus 21%). At 1 year, 96% and 78% of survivors in the earlier and later study groups, respectively, had recovery of renal function. The mean total APACHE II score was the same in both study periods, but patients in the later group were older and had more APACHE II points for chronic health problems. In the earlier and later study groups, patients with an APACHE II score of 21 or lower had a mortality rate of 36% and 11%, respectively, and survival among those with a score of 34 or greater was 0% and 15%, respectively. In 1991 and 1992, more patients had two or more factors contributing to the development of ARF, and intravenous administration of a contrast agent and preexisting cardiac prerenal compromise were more frequent causes of ARF than in 1977 through 1979. The occurrence of sepsis and preexisting lung disease were associated with a dismal prognosis in both study periods. In 1991 and 1992, survival was improved for patients with preexisting diabetes mellitus, postoperative status, and contrast-induced renal failure.

CONCLUSION

The prognosis of ICU patients with ARF has improved in more recent years, despite the fact that patients are now older, have more preexisting chronic health conditions, and have an increasing number of conditions contributing to development of ARF. The APACHE II scoring system demonstrated utility for quantifying the complexity of illness in these patients, but several important shortcomings may limit its usefulness as a comparative or prognostic tool in patients with ARF.

Treatment of surgical and non-surgical septic multiorgan failure with bicarbonate hemodialysis and sequential hemofiltration

OBJECTIVE

Hospital mortality of patients with septic multiorgan failure (MOF) is still around 95%. The present study investigates whether this high mortality could be significantly reduced by the addition of sequential hemofiltration (SH) with bicarbonate hemodialysis (HD) to the currently used life supportive measures.

DESIGN

35 (18 surgical and 17 nonsurgical) patients, with 3 or more organ failures, had daily sessions of zero balance SH, for periods ranging from 2-22 days.

MEASUREMENTS AND RESULTS

SH induced significant improvement of PaO2/100 FIO2, Apache II score, MAP, as well as blood chemistry in survivors. Dying patients had less marked improvement of blood oxygenation, non-significant changes in other variables, in addition to low MAP before and after SH, as well as marked hemodynamic unstability during the procedure. The observed hospital mortality was 38% for the surgical group, and 35.3% for the medical patients (n.s.).

CONCLUSIONS

Mortality observed in this retrospective, uncontrolled study was significantly lower than that currently observed with conventional supportive therapy, with or without the addition of other forms of blood purification, e.g. CAVH and CAVHD. This improvement in results appears to be related to the property of SH to completely clear 90% of the blood from mediators of inflammation in only one passage through the hemofilter, and to better tolerance of HD done using bicarbonate buffer. A definite evaluation of this technique will be eventually reached by a programmed, appropriate sample size study, which is out of reach for one individual ICU.

Removal of platelet-activating factor in experimental continuous arteriovenous hemofiltration

OBJECTIVE

There is a positive correlation between the amount of ultrafiltration and the improved survival rate of patients with ischemia or sepsis-induced acute renal failure. Continuous arteriovenous hemofiltration (CAVH) removes vasoactive substances with a molecular weight of < 1000 daltons. This study evaluated the removal of platelet-activating factor, a lipid mediator of endotoxic shock, by CAVH with respect to kinetics, adsorption, and ultrafiltration.

DESIGN

Prospective laboratory study.

SUBJECTS

Normal human subjects.

INTERVENTIONS

Radioactive [3H] or biologically active platelet-activating factor was added to whole blood or washed blood resuspended in Tris-buffered (pH 7.2) physiologic saline with 4% human serum albumin or plasma. Whole or washed blood cells or plasma were recirculated at 100 mL/min through polysulfone hemofilters for 120 mins with ultrafiltration (condition A), without ultrafiltration (condition B), or in a static condition (condition C). Concentrations of albumin, total protein, and radioactive or biologically active platelet-activating factor in samples obtained from the blood and ultrafiltrate compartment were determined.

MEASUREMENTS

Biologically active platelet-activating factor was quantified on washed rabbit platelets and results were expressed in ng/mL over a calibration curve obtained with synthetic platelet-activating factor.

MAIN RESULTS

[3H]-platelet-activating factor added to recirculated whole blood was ultrafiltered (percent of ultrafiltered platelet-activating factor/min: 0.48 +/- 0.02 [SD]; total platelet-activating factor removed in 120 mins: 15.52%; condition A) at significantly (p < .001) higher amounts than when added to washed blood cells (percent of ultrafiltered platelet-activating factor removed/min: 0.195 +/- 0.06; total platelet-activating factor removed in 120 mins: 7.46%). The highest amounts of [3H]-platelet-activating factor were bound to polysulfone membranes after recirculation with whole blood (44.5 +/- 12.2%) than with washed blood (1.1 +/- 0.3%) or plasma (11.9 +/- 0.7%). Biologically active platelet-activating factor concentrations significantly decreased in both conditions A and B (maximal decrease at 120 mins: 63% and 59%, respectively). No significant reduction could be observed in condition C.

CONCLUSIONS

These studies provide experimental evidence for the prompt, efficient removal of platelet-activating factor in CAVH and provide a possible rationale for the beneficial effect of this therapy in the development of multiple organ failure in sepsis.

Anticoagulation in patients treated by continuous venovenous hemofiltration: a retrospective study

The most adequate anticoagulation regimen during extracorporeal renal replacement therapy can be difficult to define. Two hundred fifty-five critically ill patients with a mean age (+/- SD) of 58.2 +/- 16.3 years were treated by continuous venovenous hemofiltration (CVVH) between 1986 and 1992 in our intensive care units. Blood was circulated through hemofilters, either polyacrylonitrile (AN 69; Hospal, Lyon, France) or polyamide (FH 66; Gambro, Lund, Sweden), using a roller pump and an air safety system. The patients were classified into three subgroups according to the amount of heparin needed to achieve an adequate anticoagulation (ie, prevention of extracorporeal circuit clotting without inducing a patient's bleeding tendency): group 1, 37 patients who received no heparin (14.5%); group 2, 189 patients who received 100 to 700 IU/hr of heparin (74.1%); and group 3: 29 patients who received more than 700 IU/hr of heparin (11.4%). We analyzed the filter survival, the routine coagulation parameters, and the evolution of the patients for each group. Median duration of treatment was 144 hours (range, 4 to 1,152 hours). There were no differences in requirement of heparin among the two types of membrane: AN 69 (mean +/- SD), 393 +/- 106 IU/hr v FH 66, 374 +/- 35.3 IU/hr (range, 0 to 2,000 IU/hr). There were no relationships between the amount of heparin the patients received and the mean survival of the filters (group 1, 22.1 +/- 14.8 hr; group 2, 24.7 +/- 13.2 hr; group 3, 23 +/- 9.6 hr).(ABSTRACT TRUNCATED AT 250 WORDS)

A prospective study of continuous hemodiafiltration in the management of severe acute renal failure in critically ill surgical patients

Severe acute renal failure associated with surgical disease and a highly catabolic state poses a major therapeutic challenge. Treatment by conventional dialysis or arteriovenous hemofiltration suffers from serious shortcomings. The current study assesses the clinical and biochemical impact of a newer approach (continuous hemodiafiltration) in a cohort of 60 critically ill surgical patients with severe renal failure. All patients were studied prospectively and assessed for illness severity. Their biochemical response to therapy was analyzed and their clinical course to either death or hospital discharge documented. The use of continuous hemodiafiltration (CHD) permitted full control of azotemia in all patients (mean steady-state urea concentration: 19.8 mmol/L) and was associated with rapid control of acidemia (mean pretreatment pH: 7.27; mean ph after 24-h treatment: 7.35; p < .001). During the 15,696 h of therapy, there were no treatment-induced episodes of hypotension and/or hypoxemia. All patients were able to receive full-dose enteral (9) or parenteral (51) nutritional support with 1.5 to 2.5 g/kg/day of protein as tolerated. Despite their illness severity (mean APACHE II score: 28.9) and the need for vasopressor support and ventilation in 90% of cases, 21 patients (35%) survived to hospital discharge. We conclude that continuous hemodiafiltration is safe and effective in surgical critically ill patients with acute renal failure, and that it is associated with a low morbidity and an encouraging survival rate.

A review of continuous renal replacement therapy

Patients in the Intensive Care Unit commonly develop acute renal failure (ARF). The kidneys are rarely the only organs failing in these patients. Frequently ARF is part of multiple organ dysfunction syndrome. The choice of dialytic therapy should consider, not only the efficacy of the therapy, but also the undesirable effects such therapy may have on the other failing organs. Intermittent Haemodialysis and Peritoneal Dialysis were the conventional forms of dialysis available. Both are associated with complications which may make them unsuitable for use in the haemodynamically unstable, hypercatabolic patients, seen in the Intensive Care setting. Continuous Renal Replacement Therapy (CRRT) has been introduced in many Intensive Care Units to provide a more stable, flexible form of dialysis. The purpose of this article is to give an overview of the various forms of CRRT and to discuss the advantages of this form of therapy.