CONTINUOUS RENAL REPLACEMENT THERAPY: OUR EXPERIENCE IN INTENSIVE CARE UNIT

Abstract

Continuous Renal Replacement Therapy (CRRT) indication is still discussed. We report our experience on 98 patients affected with Multiple Organ System Failure (MOSF) and renal failure (acute or chronic) requiring dialysis and timely treated by CRRT. Mortality after 5 days of ICU permanence was 60.2%; the remaining 39 patients were discharged within 21 days and received CRRT treatment for 6.36 ± 5.59 days. APACHE II score was not able to predict the outcome of patients suffering from acute renal failure (ARF). On the contrary, Systemic Inflammatory Response Syndrome (SIRS) incidence was significantly higher in deceased patients compared to recovered patients.

In conclusion, it is important to start dialytic treatment immediately when patients affected with MOSF show renal function damage, even if at an initial stage, in order to improve patients' survival. Moreover a multidisciplinary approach is preferable in ICU patients treatment for not underestimating the management of metabolic and infective complications, the nursing care, and nutritional support.

INTRODUCTION

Renal failure requiring renal replacement therapy is a common problem in Intensive Care Unit (ICU). The mortality of patients affected with Multiple Organ System Failure (MOSF) remains high despite advances in renal supportive therapy [1-2]. In the acute ICU setting, traditional hemodialysis leads to several disadvantages because of hemodynamic instability and hypotension in critically ill patients. Continuous Renal Replacement Therapy (CRRT), instead, possesses several theoretical advantages, including slow and continuous therapy and ease of initiation and maintenance in the intensive care setting [3-4].

We report our experience on 98 patients affected from MOSF and acute or chronic renal failure requiring dialysis, treated early by CRRT.

MATERIALS AND METHOD

98 selected patients (January 1996–November 1999), affected from MOSF and requiring hemodialytic treatment entered our study. Severity of illness and risk of death were calculated for each patient using APACHE II score at ICU admittance. Etiology for each patient is shown in Fig. 1. In acute renal failure (ARF) patients CRRT was started immediately when sCr was > 3.5 mg/dL and urine flow/24 hrs < 500 mL despite forced diuresis. CRRT was started within 24 hrs from ICU admittance in patients on chronic hemodialysis.

Figure 1. Basic pathologies subtended to MOSF.

Venous vascular access was obtained generally by cannulation of the femoral vein by a double-lumen catheter. Anticoagulation of circuit was achieved by continuous heparin infusion (300–600 U/hr) in the arterial limb and monitored by measurement of activated clotting time on systemic blood samples (12 hrs). Acrylonitrile filters were used (0.4 ± 0.1 m²). The circuit was replaced every 48 hrs (24 hrs in septic patients) in case of clotting. Ultrafiltration was automatically aimed at 100 ± 60 mL/hr by dialysis machine (Prisma Hospal). Fluid balance was adjusted every hour. Blood pump speed was 100 ± 0.50 mL/min and dialysate flow was 1500 ± 500 mL/hr.

End stage renal disease (ESRD) on hemodialysis, renal function recovery and renal function stability (sCr, BUN, electrolytes and acid-base balance stability after 24 hrs from CRRT stoppage) were considered the end-points.

Nutritional status was preserved by enteral or total parenteral nutrition. Predialytic and subsequently daily blood samples were drawn. Biochemical and clinical data were collected. We also evaluated Systemic Inflammatory Response Syndrome (SIRS) presence. The term “SIRS” indicates a clinical response, despite etiology. Two or more of the following criteria were needed to identify SIRS presence: body temperature > 38°C or < 36°C; heart rate > 90 bpm; respiratory rate > 20 breaths/min or PaCO² < 32 mmHg; WBC > 12,000/mm³ or < 4,000).

Results are expressed by mean values and standard deviations. In statistical test, a p value < 0.05 was considered significant.

RESULTS

We observe that out of 98 patients selected, 68.4% were males. The mean age was 65.14 ± 12.76 yrs (range: 27–89). 59 patients died (60.2%) after 5.29 ± 6.03 days, the remaining 39 were discharged from ICU within 21 days (range: 8–30) and received CRRT treatment for 6.36 ± 5.59 days.

Our results are summarized in Table 1. Among 35 ARF survived patients, 3 showed a complete recovery of renal function, 9 were suffering from light renal failure (sCr < 2.5 mg/L) and 13 were affected with moderate (sCr < 5 mg/dL) renal failure, while in the 10 remaining patients severe renal failure persisted. Among patients on maintenance dialysis before the hospitalization, 6 died (60%) and 4 recovered.

Table

	Age MV ± SD	Sex %	APACHE II MV ± SD	SIRS %	CRRT Days MV ± SD
All pts	65.14 ± 12.76	F: 31.6	29.08 ± 7.62	68.33	5.71 ± 5.85
98	(range 25–89)	M: 68.4	(range 7–48)		(range 1–18)
Recovered	61.44 ± 14.12	F: 35.9	27.10 ± 6.62	29.85	6.36 ± 5.59
39 (39.8%)	(range 27–86)	M: 64.1	(range 7–41)		(range 2–18)
Died	67.59 ± 11.25	F: 33.9	29.39 ± 7.24	70.10	5.10 ± 6.03
59 (60.2%)	(range–2589)	M: 66.1	(range 13–48)		(range 1–14)

We found a significantly higher mean age in deceased patients compared to recovered ones (67.59 ± 11.25 vs 61.44 ± 14.12 respectively: p = 0.019). We found no statistical difference between survival and deceased patients considering APACHE II score, while SIRS incidence was significantly higher (p = 0.027) in deceased patients compared to the recovered ones (39 SIRS patients on 59 deceased patients; 15 SIRS patients on 39 survived patients).

In regards to APACHE II score, we found no significant correlation with patients' general mortality, while dividing patients into two groups (APACHE II > 30 and APACHE II < 30) we observed a significant correlation (p < 0.05) (Fig. 2). However, these criteria were not able to predict outcome in ARF.

Figure 2. Percentage of died and recovered subjects in the studied population divided into SIRS/NOSIRS patients, with APACHE II score <30 and >30 (p < 0.05).

DISCUSSION

At the moment, the onset of ARF represents one of the most jeopardizing events for ICU patients. Patients with ARF and MOSF have a compromised circulation with secondary serious hypotension and/or cardiac arrhythmia: consequently insufficient amount of fluid is removed and progressive fluid and electrolyte imbalances ensue. It is important to identify the less damaging hemodialysis modality in high-risk patients affected with MOSF. Moreover, in ICU patients the presence of chronic renal failure on maintenance hemodialysis dramatically complicates the care of these patients. Bommell and Ponssen observe that the outcome of ARF patients has remained similar to that observed two or more decades ago [[5]]. Generally, in ICU patients dialysis is not a cure, but it simply replaces renal function. Intermittent dialysis can correct biochemical abnormalities and remove the fluid excess in a short time, but it can cause hypovolemia and hypokalemia. Hypotension and ultrafiltration contribute to further renal damage. Often fluid removal is suboptimal, resulting in the persistence of oedema [[6]]. CRRT has been introduced in many ICUs to provide a form of dialysis allowing to keep a better hemodynamic stability.

In this study, we reported our experience on CRRT in 98 patients admitted in ICU for different causes and requiring renal function replacement. To estimate the prognosis we evaluated specific parameters by severity-of-disease classification systems. According to other authors the prognostic value of APACHE II is not decisive [[7]]. Liano et al, [[8]] found that in 228 patients with ARF the most important factor contributing to death was the underlying cause of ARF. Recently Schwilk et al. [[7]] observed that general measures of severity are not useful in predicting the outcome of ARF. Only the etiology, the number of dysfunctioning organ systems, massive transfusions and patients' age give a reliable prognosis. We observe a significant age difference between deceased patients and recovered ones. It is not yet clear whether CRRT can improve the outcome of ICU patients affected with ARF.

Adequate nutritional support may impact a positive outcome. Catabolic, renal failure patients have a high incidence of morbidity and mortality. Immediate enteral (or parenteral) nutrition stimulates the splanchnic and hepatic circulation, improves mucosal blood flow and decreases permeability disturbances [[9]]. Nutrient deficiencies can impair immune response. MOSF and SIRS patients do not die from infection but from their own inflammatory response but pathophysiology has not been completely clarified. The problem of these syndromes is an excessive reaction of the inflammatory response system to bacterial or nonbacterial stimuli. Goris [[10]] suggests to prevent all conditions favoring SIRS and MOSF (infections, hypoxemia, tissue hypoxia, and any factor activating inflammatory cascade systems) and to modulate the inflammatory response system of phagocytes. He suggests that MOSF and SIRS are the consequence of apoptosis failure in phagocytes when their action is no longer required. Cytokines, complement and other inflammatory mediators are removed by convection or adsorption by hemofilters utilized in CRRT [[11]]. Ronco et al. [[12]] have considered a combined technology system (hemofiltration/cytokine-absorbing resins) in order to decrease cytokines and cytokine-inducing compounds plasma levels.

Randomized studies would be necessary to clearly demonstrate CRRT benefits in comparison with intermittent dialysis treatment. Treatment choice in acute renal failure should be based on a single patient's needs and on available therapies features: availability of access, bleeding risk, hemodynamic stability and ability to remove excess fluid.

The difference between CRRT and intermittent hemodialysis costs are not so great, considering that CRRT supervision is delegated to the responsible ICU nurse without additional labor cost. The intensive care setting is well recognized as a highly technical area, and selected nurse staff are introduced continually to new equipment without a hitch.

In conclusion, CRRT was promising for a better control of the uremic syndrome. It is also important not to underestimate the management of metabolic and infective complications, the nursing care, and the nutritional support. Apart from the dialytic technique choice, a careful interdisciplinary monitoring is needed for MOSF and ARF patients' survival.