Extracorporeal treatment of acute renal failure in the intensive care unit: a critical view

Filter lifetimes of different hemodiafiltration membrane materials in dogs: reevaluation of the optimal anticoagulant dosage

Background

In continuous renal replacement therapy (CRRT), administration of anticoagulants is necessary for achieving a certain level of filter lifetime. Generally, anticoagulant doses are controlled to keep activated partial thromboplastin time and other indicators within a certain target range, regardless of the membrane materials used for the filter. However, in actual clinical practice, the filter lifetime varies significantly depending on the membrane material used. The objective of this study was to demonstrate that the minimum anticoagulant dose necessary for prolonging the filter lifetime while reducing the risk of hemorrhagic complications varies depending on the type of membrane.

Methods

In three beagles, hemodiafiltration was performed with hemofilters using polysulfone (PS), polymethylmethacrylate (PMMA), and AN69ST membranes separately. The minimum dose of nafamostat mesylate (NM) that would allow for 6 h of hemodiafiltration (required dose) was investigated for each membrane material.

Results

The NM doses required for 6 h of hemodiafiltration were 2 mg/kg/h for the PS membrane, 6 mg/kg/h for the PMMA membrane, and 6 mg/kg/h for the AN69ST membrane.

Conclusion

For hemodiafiltration performed in beagles, the required NM dose varied for each filter membrane material. Using the optimal anticoagulant dose for each membrane material would allow for safer CRRT performance.

Ability of nafamostat mesilate to prolong filter patency during continuous renal replacement therapy in patients at high risk of bleeding: a randomized controlled study

Continuous renal replacement therapy (CRRT) is considered as an effective modality for renal replacement therapy in hemodynamically unstable patients within intensive care units (ICUs). However, the role of heparin anticoagulation, which is used to maintain circuit patency, is equivocal due to the risk of bleeding and morbidity. Among various alternative anticoagulants, nafamostat mesilate has been shown to be an effective anticoagulant in patients prone to bleeding. Hence, we conducted a prospective, randomized controlled study investigating the effect of nafamostat mesilate on mortality, CRRT filter life span and adverse events in patients with bleeding tendency. Seventy-three Patients were randomized into either the futhan or no-anticoagulation group. Thirty-six subjects in the futhan group received nafamostat mesilate, while thirty seven subjects in the no-anticoagulation group received no anticoagulants. Baseline characteristics and appropriate laboratory tests were taken from each group. The mortality between the two groups was not significantly different. Nevertheless, between the futhan group and the no-anticoagulation group, the overall number of filters used during CRRT (2.71 ± 2.12 vs. 4.50 ± 3.25; p = 0.042) and the number of filters changed due to clots per 24 hours (1.15 ± 0.81 vs. 1.74 ± 1.62; p = 0.040) were significantly different. When filter life span was subdivided into below and over 12 hours, the number of filters functioning over 12 hours was significantly higher in the futhan group than in the no-anticoagulation group (p = 0.037, odds ratio 1.84). There were no significant differences in transfusion, mortality, or survival between the two groups, and no adverse events related to nafamostat mesilate were noted. Hence, nafamostat mesilate may be used as an effective and safe anticoagulant, without increasing the risk of major bleeding complications, in patients prone to bleeding.

TRIAL REGISTRATION

Clinicaltrials.gov NCT01761994.

Population pharmacokinetics of fluconazole in critically ill patients receiving continuous venovenous hemodiafiltration: using Monte Carlo simulations to predict doses for specified pharmacodynamic targets

Fluconazole is a widely used antifungal agent that is extensively reabsorbed in patients with normal renal function. However, its reabsorption can be compromised in patients with acute kidney injury, thereby leading to altered fluconazole clearance and total systemic exposure. Here, we explore the pharmacokinetics of fluconazole in 10 critically ill anuric patients receiving continuous venovenous hemodiafiltration (CVVHDF). We performed Monte Carlo simulations to optimize dosing to appropriate pharmacodynamic endpoints for this population. Pharmacokinetic profiles of initial and steady-state doses of 200 mg intravenous fluconazole twice daily were obtained from plasma and CVVHDF effluent. Nonlinear mixed-effects modeling (NONMEM) was used for data analysis and to perform Monte Carlo simulations. For each dosing regimen, the free drug area under the concentration-time curve (fAUC)/MIC ratio was calculated. The percentage of patients achieving an AUC/MIC ratio greater than 25 was then compared for a range of MIC values. A two-compartment model adequately described the disposition of fluconazole in plasma. The estimate for total fluconazole clearance was 2.67 liters/h and was notably 2.3 times faster than previously reported in healthy volunteers. Of this, fluconazole clearance by the CVVHDF route (CL(CVVHDF)) represented 62% of its total systemic clearance. Furthermore, the predicted efficiency of CL(CVVHDF) decreased to 36.8% when filters were in use >48 h. Monte Carlo simulations demonstrated that a dose of 400 mg twice daily maximizes empirical treatment against fungal organisms with MIC up to 16 mg/liter. This is the first study we are aware of that uses Monte Carlo simulations to inform dosing requirements in patients where tubular reabsorption of fluconazole is probably nonexistent.

Quantification of creatinine kinetic parameters in patients with acute renal failure

BACKGROUND

Urea kinetic modeling (UKM) and creatinine (Cr) kinetic modeling (CKM) are used in the nutritional evaluation of end-stage renal disease (ESRD) patients. Both the UKM-derived normalized protein catabolic rate (nPCR) and the CKM-derived estimate of lean body mass (LBM) may also provide important information in critically ill acute renal failure (ARF) patients. Estimation of LBM may be particularly useful as previous data demonstrate that malnutrition adversely influences outcome in ARF patients.

METHODS

Eleven critically ill ARF patients (age 52 +/- 21 years; mean +/- SD) treated with continuous venovenous hemofiltration (CVVH) were the study group. They were analyzed at steady state with a single-pool variable-volume model that determined the creatinine generation rate (GCr) by a methodology that we have previously described.

RESULTS

The CVVH ultrafiltrate production rate was 913 +/- 49 ml/hr, yielding a blood Cr clearance of 15.2 +/- 0.9 ml/min and a steady state serum Cr of 3.4 +/- 1.7 mg/dl. Daily creatinine generation normalized to body wt (creatinine index: CI) was 6.3 +/- 0.8 and 10.6 +/- 3.0 mg/kg/day for females (N = 4) and males (N = 7), respectively (P < 0.05). Estimated mean LBM was 30.0 +/- 2.0 and 41.2 +/- 7.0 kg in females and males, respectively (P < 0.05), while the same parameter normalized to body wt was 0.50 +/- 0.05 and 0.52 +/- 0.10, respectively. These values are substantially lower than those previously reported for both normal and ESRD patients. Regression analysis demonstrated both GCr (r2 = 0.96; P < 0.001) and LBM (r2 = 0.96; P < 0.001) were significantly correlated with steady state serum Cr in a linear manner. However, no significant correlation (r2 = 0.06; P = 0.24) between nPCR and CI was observed.

CONCLUSIONS

These data suggest critically ill ARF patients have severe somatic protein depletion. This malnourished state is likely due to deficits established prior to the development of ARF, such as those secondary to underlying chronic illnesses or prolonged hospitalization, and deficits related to acute hypercatabolism. Quantitative assessment of malnutrition in ARF patients with this CKM-based methodology may permit a better understanding of predisposing factors and, consequently, facilitate the development of interventions designed to prevent malnutrition in these patients.

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.

Intermittent hemodialysis in critically ill patients with multiple organ dysfunction syndrome is associated with intestinal intramucosal acidosis

OBJECTIVE

Conventional intermittent hemodialysis in the critically ill patient can be associated with hemodynamic and respiratory instability. Intermittent hemodialysis induced arterial hypotension might be detrimental. We therefore studied the influence of intermittent hemodialysis on systemic and regional oxygen transport in critically ill patients.

DESIGN

Prospective descriptive study.

SETTING

Medical/surgical 24-bed intensive care unit in a university hospital.

PATIENTS

Eleven critically ill patients admitted to the intensive care unit (APACHE III score: 82 +/- 12) and developing multiple organ dysfunction syndrome with acute renal failure. All patients were mechanically ventilated and hemodynamically stable with inotropic support. Systemic oxygen transport variables were calculated, and arterial blood lactate concentration was measured before, during, and after intermittent hemodialysis. Tonometer PCO2 was measured using a tonometer, and arterial-tonometer CO2 gap was used as an indicator of intestinal intramucosal acidosis.

RESULTS

Intermittent hemodialysis induced an increase in calculated systemic oxygen consumption (P < 0.01). During intermittent hemodialysis there was a significantly higher need of inotropic support (P < 0.05) to maintain arterial blood pressure, cardiac index, and calculated systemic arterial oxygen delivery. The arterial-tonometer CO2 gap increased significantly during and after the procedure.

CONCLUSION

In critically ill patients with multiple organ dysfunction syndrome intermittent hemodialysis induces an increase in oxygen consumption. Despite higher inotropic support to maintain systemic calculated oxygen delivery intestinal intramucosal acidosis occurs during intermittent hemodialysis and may even persist after the procedure is terminated.

Glucose dynamics during continuous hemodiafiltration and total parenteral nutrition

OBJECTIVE

To determine glucose balance during dextrose-free continuous hemodiafiltration with or without dextrose-containing ultrafiltrate replacement fluid and full nutritional support.

DESIGN

Prospective, nonrandomized, observational study.

SETTING

A 24-bed multiple trauma critical care unit in a level-I trauma center.

PATIENTS

Seventeen multiple trauma patients with multiple organ dysfunction syndrome requiring hemodialysis for acute renal failure.

INTERVENTIONS

Continuous hemodiafiltration effluent volume and glucose concentration were measured. Study days were classified according to whether dextrose was used in the ultrafiltrate replacement therapy. Use of dextrose in replacement therapy was determined clinically. Parenteral nutrition was not altered for potential glucose absorption from continuous hemodiafiltration. Ultrafiltrate replacement consisted of 5% dextrose in saline on 21 study days (D5YES) and dextrose-free solutions on 54 study days (D5NO).

RESULTS

The D5YES group received 316 +/- 145 g glucose/day from the ultrafiltrate replacement fluid, in addition to glucose in total parenteral nutrition (total glucose intake = 942 +/- 229 g/day in D5YES, 682 +/- 154 g/day in D5NO) (p < 0.05). Glucose loss in continuous hemodiafiltration effluent was 82 +/- 61 g/day in D5YES and 57 +/- 22 g/day in D5NO (P < 0.05), for a net glucose uptake of 8.1 +/- 2.1 mg/kg per min in D5YES and 5.4 +/- 1.5 mg/kg per min in D5NO (p < 0.05). Glucose loss was predictable when dialysate and ultrafiltrate replacement fluids were dextrose-free (R2 = 0.77), but less so when dextrose was used as ultrafiltrate replacement (R2 = 0.47).

CONCLUSION

Dextrose-free dialysate promotes glucose loss during continuous hemodiafiltration, but the loss is small and predictable. Use of a dextrose-containing ultrafiltrate replacement fluid results in a significant increase in glucose intake without a commensurate increase in glucose loss, and makes glucose loss in effluent less predictable.

Continuous renal replacement therapy for critically ill patients: an update

Despite continuous progress in intensive care during the last decades, the outcome of critically ill patients in whom acute renal failure (ARF) develops is still poor. This outcome may be explained partially by the frequent occurrence of ARF as part of multiple organ systems failure (MOSF). In this complex and unstable patient population, the provision of adequate renal support with either intermittent hemodialysis or peritoneal dialysis may pose major problems. Continuous renal replacement therapy (CRRT) is now increasingly accepted as the preferred treatment modality in the management of ARF in these patients. The technique offers adequate control of biochemistry and fluid balance in hemodynamically unstable patients, thereby enabling aggressive nutritional and inotropic support without the risk of exacerbating azotemia or fluid overload. In addition, experimental and clinical data suggest that CRRT may have a beneficial influence on hemodynamics and gas exchange in patients with septic shock and (nonrenal) MOSF, independent of an impact on fluid balance. We review both technical and clinical aspects of various continuous therapies, including their impact on serum drug levels and nutrient balance. In addition, an attempt is made to clarify the possible beneficial role of CRRT in reducing patient morbidity and mortality in the ICU.

Influence of continuous haemofiltration-related hypothermia on haemodynamic variables and gas exchange in septic patients

OBJECTIVE

To investigate the influence of continuous haemofiltration (CHF) on haemodynamics, gas exchange and core temperature in critically ill septic patients with acute renal failure.

PATIENTS AND METHODS

In 20 patients (17 male, 3 female) ultrafiltration rate, core temperature, gas exchange and haemodynamic variables were measured at regular intervals during the first 48 h of haemofiltration. Baseline data were compared to those obtained 30 min after initiating CHF and also to those during hypothermia (if observed).

MAIN RESULTS

Haemodynamic variables remained remarkably constant throughout the study period. In patients with a relatively low ultrafiltration rate (855 +/- 278 ml/h) temperature did not change, while in patients with a high ultrafiltration rate (1468 +/- 293 ml/h) core temperature significantly decreased from 37.6 +/- 0.9 degrees C to 34.8 +/- 0.8 degrees C (p < 0.001). There was a statistically significant correlation between temperature decrease and ultrafiltration rate (r = -0.68, Y = 1.8-0.003 X, p < 0.01). Hypothermic patients also showed a mean decrease in VO2 from 141 +/- 22 ml/min/m2 to 112 +/- 22 ml/min/m2 (p < 0.01) with a concomitant increase in PaO2 from 103 +/- 37 mmHg to 140 +/- 42 mmHg (p < 0.001) and in PvO2 from 35 +/- 4 mmHg to 41 +/- 5 mmHg (p < 0.001).

CONCLUSIONS

1) Continuous haemofiltration does not cause significant alternations in haemodynamic variables. 2) Hypothermia frequently occurs in patients undergoing continuous haemofiltration with high ultrafiltration rates. These hypothermic patients show a reduction in VO2 leading to an increase in PvO2 and PaO2. This mild hypothermia in these circumstances has no evident deleterious effects.

Heparin clearance during continuous veno-venous haemofiltration

OBJECTIVE

To determine whether premature clotting of haemofiltration circuits could be related to heparin removal across the filter membrane into the ultrafiltrate.

DESIGN

Randomised study using either unfractionated (n = 8) or low molecular weight (n = 7) heparin for anticoagulation of the haemofiltration circuit at 1000 and 600 U/h respectively. Samples were drawn at 1 and 2 h from arterial and venous limbs of the haemofilter circuit for measurement of plasma heparin (as anti-Factor Xa activity), antithrombin III and haematocrit. Ultrafiltrate samples were collected at the same time for measurement of anti-Xa activity.

SETTING

Intensive care unit.

PATIENTS

Patients in acute renal failure requiring haemofiltration.

RESULTS

Both unfractionated and low molecular weight heparin plasma levels were within the range required for therapeutic anticoagulation in all but one patient at 2 h. Ultrafiltrate anti-Xa levels were insignificant. Antithrombin III levels in these critically ill patients were subnormal in 11 of the 15 studies.

CONCLUSIONS

Despite their small sizes, neither unfractionated nor low molecular weight heparins cross the haemofilter membrane into the ultrafiltrate in any measurable quantity. Both heparins were present in plasma at a level suitable for therapeutic anticoagulation. Subnormal levels of antithrombin III may be an important factor in determining filter longevity.

Anticoagulant regimens in acute continuous hemodiafiltration: a comparative study

OBJECTIVE

To compare and contrast different heparin regimens for extracorporeal circuit anticoagulation in patients receiving acute continuous hemodiafiltration (ACHD).

DESIGN

Prospective controlled randomized comparisons of the following regimens: 1) Low dose (500 IU/h) pre-filter heparin versus regional anticoagulation in patients on continuous arteriovenous hemodiafiltration (CAVHD) via A-V shunt. 2) Low dose pre-filter heparin versus no anticoagulation in patients receiving CAVHD via femoral cannulae. 3) Low dose pre-filter heparin versus regional anticoagulation in patients on continuous veno-venous hemodiafiltration (CVVHD). 4) An assessment of the consequences of the use of no anticoagulant in patients predicted to be at high risk of hemorrhagic complications on treatment with CVVHD.

SETTING

University Teaching Hospital ICU.

PATIENTS

64 ICU patients with acute renal failure.

MEASUREMENTS AND MAIN RESULTS

Haemofilter survival during shunt CAVHD was significantly prolonged by the use of regional anticoagulation compared to the use of low dose heparin (mean filter survival: 57.1 h versus 42.9 h; p < 0.05). In CAVHD using femoral cannulae, no significant differences in haemofilter survival were found between anticoagulation with low dose heparin and the use of no anticoagulant (mean filter survival: 55 h versus 52.5 h; NS). During CVVHD, regional anticoagulation compared to low dose heparin produced a trend towards prolonged filter life which was, however, not statistically significant (mean filter survival: 40.5 h versus 31.4 h; NS). In patients assessed to be at high risk of bleeding, CVVHD without anticoagulation provided a mean filter survival of 40.9 h (95% CI 27-54.8 h).

CONCLUSIONS

Regional anticoagulation leads to longer filter survival than low dose heparin in shunt CAVHD. A regimen of no anticoagulation during femoral CAVHD leads to a filter life similar to that of low dose heparinization. During CVVHD, regional anticoagulation and low dose heparin are associated with similar filter survival times. In patients assessed to be at high risk of bleeding, treatment with CVVHD without anticoagulation results in adequate filter survival.

Continuous veno-venous haemofiltration following cardio-pulmonary bypass. Indications and outcome in 35 patients

OBJECTIVE

To study the impact of continuous veno-venous haemofiltration on survival in patients with acute renal failure (ARF) following cardio-pulmonary bypass (CPB) surgery.

DESIGN

A retrospective study of all patients requiring haemofiltration after CPB over a 2 year period.

SETTING

A 20 bedded, adult cardothoracic intensive care unit in a postgraduate teaching hospital.

PATIENTS

35 patients (26 male, age range 24-74 years) required haemofiltration (2.7% of the total number of patients undergoing CPB).

MAIN RESULTS

Cardiovascular failure post CPB was the commonest causes of ARF (n = 16). Indications for haemofiltration were uremia (21), oligo-anuria (11), volume overload (2) and hyperkalaemia (1). Mean time from CPB to the initiation of haemofiltration was 8 days (range 0-15 days). Mean urea was 30 mmol/l and creatinine 362 mumol/l immediately prior to treatment. Urea was well-controlled in all patients, although 2 needed haemodiafiltration. Twenty-six patients died during their admission to the ICU (74% mortality). A further 3 patients died during their hospital admission, following discharge from ICU. Outcome was particularly poor in patients with cardiovascular failure following CPB (16 cases, 0 survivors). Survivors tended to commence filtration earlier (mean of 4 vs 7 days for non-survivors) and required treatment for a mean period of 8 days (range 1-26 days). Survival was determined by the number of failed organ systems at the start of haemofiltration. Thus, 100% of patients with single system failure survived, compared to only 10% with 3 or more system failure.

CONCLUSIONS

Despite the theoretical advantages of haemofiltration and the effective control of uraemia the mortality associated with ARF following CPB remains high and is probably determined by the number of failed organs systems.

Full protein alimentation and nitrogen equilibrium in a renal failure patient treated with continuous hemodiafiltration: a case report of 67 days of continuous hemodiafiltration

Standard care for patients with renal failure while in an intensive care unit involves traditional hemodialysis or peritoneal dialysis and protein restriction. We present a case of a patient with renal failure supported with continuous arteriovenous hemofiltration with dialysis (CAVH-D) who was given full protein alimentation. Total daily urea clearance was measured from the CAVH-D output. Protein load was 196 +/- 34 g/day while receiving total parenteral nutrition and 164 +/- 30 g/day while receiving enteral alimentation. Serum blood urea nitrogen was controlled between 40 and 75 mg/dL, except during septic episodes. Nitrogen balance was estimated based upon known alimentation protein load and measurable and estimated nitrogenous losses. The patient was potentially in nitrogen equilibrium during most of the dialysis period. The cumulative nitrogen balance was positive by 5.2 g after 67 days of dialysis. Volume of alimentation was 3.49 +/- 0.7 liters/day. With CAVH-D, the renal failure patient can receive full alimentation without volume or protein load limitations. Furthermore, nitrogen balances can be estimated easily while the patient is on CAVH-D.

Progressive hypercalcemia during continuous arterio-venous ultrafiltration (SCUF)

A case report is described of a patient who developed severe hypercalcemia during slow continuous arterio-venous ultrafiltration (SCUF). Which was instituted because of refractory congestive heart failure with pulmonary edema. The hypercalcemia was due to a preexisting mild hyperparathyroidism and aggressive fluid removal by SCUF. The differential diagnosis of hypercalcemia in the intensive care ward is discussed.

Five years experience with continuous extracorporeal renal support in paediatric intensive care

Continuous arterio-venous haemofiltration (CAVH) and continuous veno-venous haemofiltration (CVVH) were used as renal support in 52 critically ill infants and children with acute renal failure. The majority of the patients were on mechanical ventilation (90%) and needed vasopressor support (85%). Uraemia was satisfactorily controlled with both treatment modes. Post-treatment serum urea levels were not different between survivors (94 +/- 8.8 mg/dl) and non-survivors (99.5 +/- 8.8 mg/dl). There were significant differences between survivors and non-survivors in the mean arterial pressure (64.7 +/- 3.8 vs 48.0 +/- 2.2 mmHg, p less than 0.001), the number of organ system failures (2.9 +/- 0.16 vs 3.8 +/- 0.21, p less than 0.025), and the severity of illness assessed by the acute physiologic score for children (APSC 19.4 +/- 1.9 vs 26.3 +/- 1.9, p less than 0.01). The overall mortality was 48%. The mortality in the CVVH group (65%) was higher than in the CAVH group (40%). Death was significantly related to sepsis (p less than 0.005) and multiple system organ failure (p less than 0.005). A major complication during CAVH was one femoral artery thrombosis after 12 days of treatment. Technical problems were only observed during CVVH. CAVH and CVVH are safe and effective methods of continuous renal support for critically ill paediatric patients with multiple system organ failure. CAVH is simpler, needs no specially trained staff and seems to the ideal renal replacement system for critically ill infants.

The haemodynamic effects of intermittent haemofiltration in critically ill patients

The haemodynamic effects of intermittent high volume venovenous haemofiltration were studied in 13 critically ill patients. The mean negative fluid balance during filtration was 1.21 and the mean duration of treatment 3 h 40 min. The cardiac index fell initially (4.5 +/- 0.2 to 3.8 +/- 0.21/min/m2; p less than 0.05) but then remained stable throughout treatment before returning to baseline at the end of haemofiltration. The mean arterial pressure was unchanged with an increase in the systemic vascular resistance (651 +/- 33 to 765 +/- 65 dyne.s/cm5; p less than 0.05) suggesting that vascular responsiveness is maintained during haemofiltration.

The consequences of continuous haemofiltration on lung mechanics and extravascular lung water in a porcine endotoxic shock model

Endotoxinaemia (E. coli endotoxin, 0.111.B4) and pulmonary hypertension were evoked in 20 swine, randomly assigned to receive either zero-balanced venovenous haemofiltration (HF) with an ultrafiltration and replacement rate of 600 ml/h (HF group, n = 10) or to undergo an uninfluenced spontaneous course (E group, n = 10) during a constant infusion of endotoxin until the end of the experiment. Endotoxin-induced pulmonary dysfunction was assessed on the basis of extravascular lung water (EVLW) using a thermo-dye technique via a fiberoptic intra-aortic probe, gas exchange and lung mechanics, the latter derived by a pressure-volume loop (P/V loop) of the respiratory system (super syringe, flow 30 ml/s, tidal volume 600 ml). A comparable increase in alveolo-arterial oxygen difference and a constant EVLW was observed in both groups. The progressive deterioration of hysteresis area and compliance parameters by endotoxinaemia was significantly blunted by HF. Independent of an impact on pulmonary oedema zero-balanced HF modifies endotoxin induced lung injury, probably by the convective transport of mediator substances.

Comparison of pump-driven and spontaneous continuous haemofiltration in postoperative acute renal failure

In a comparison of spontaneous continuous arteriovenous haemofiltration (CAVH) and pump-driven haemofiltration (PDHF) for acute renal failure after surgery, 116 patients admitted to a surgical intensive care unit were assigned CAVH (48) or PDHF (68). The method of assignment was that a patient was treated by PDHF if he or she was the only patient requiring treatment at that time (only one pump was available); any other patient coming to the unit would be treated by CAVH. The groups were slightly unbalanced because there were fewer simultaneous cases than expected. The main endpoints were survival rate, control of uraemia, and additional application of haemodialysis. There were no differences between the patient groups in age, duration of treatment, severity of illness, serum creatinine concentration at the start of treatment, or cause of acute renal failure. Both treatments adequately controlled uraemia and fluid overload. However, the survival rate was significantly higher with PDHF than with CAVH (6 [12.5%] vs 20 [29.4%]; p less than 0.05). The daily ultrafiltrate volume was significantly higher with PDHF than with CAVH (15.7 [95% confidence interval 13.6-17.8] vs 7.0 [6.6-7.4] l/day; p less than 0.05). The volume of ultrafiltrate in patients with ischaemic or sepsis-induced acute renal failure was correlated with the survival rate. This finding suggests that the better survival rate in the PDHF group was due to faster elimination of toxic mediators (of molecular weight 800-1000 daltons) through the filter membrane by high-volume haemofiltration.

Influence of continuous haemofiltration on haemodynamics and central blood volume in experimental endotoxic shock

In order to assess the influence of continuous haemofiltration (HF) on haemodynamics and central blood volume in endotoxic shock, endotoxinaemia was invoked in 20 swine (28-32 kg). 15 min after doubling the mean pulmonary pressure, the animals were randomly assigned to receive either a zero-balanced veno-venous HF with an ultrafiltration and replacement rate of 600 ml/h (HF group, n = 10) or to observe the spontaneous course (E group, n = 10) under a constant infusion of endotoxin for 4 h. A trend to a higher survival rate in the HF group (6/10 vs. 3/10; E group) during the observation period was evident, but not statistically significant. Early initiation of HF during endotoxic shock modifies the haemodynamic response, lowering the pulmonary artery pressure (PAP), PCWP, pulmonary (PVR) and systemic vascular resistance (SVR), compared to the spontaneous course, whereas the decrement of central blood volume was comparable in both groups. These changes cannot be explained by effects of the HF on the volume status, but supports and additional effect by the filtration of small and medium-sized molecules.