Continuous veno-venous haemofiltration in adult intensive therapy
*Grzegorz Kluczewski1, Danuta Gierek1, Adriana Kaczmarska1, Tomasz Cyzowski1, Józefa Dąbek2, Łukasz Krzych3
1Department of Anaesthesiology and Intensive Therapy, Medical University of Silesia in Katowice
22nd Department of Cardiology, Medical University of Silesia in Katowice
31st Department of Cardiac Surgery, Medical University of Silesia in Katowice
Background. Continuous veno-venous haemofiltration (CVVH) has been recommended for renal replacement therapy in acute renal failure (ARF). The aim of the study was to analyse the usefulness of CVVH in intensive therapy settings.
Methods. Sixteen adult patients, treated with CVVH because of ARF complicating multiple organ failure, were allocated to two groups: those who survived and those who did not. Serum lactate, creatinine, potassium, and C-reactive protein concentrations, together with WBC count and arterial blood gases, were assessed before the start of CVVH, and daily during the therapy. The severity of the patients’ clinical state was rated according to the Sepsis-related Organ Failure Assessment scale (SOFA) at both the initiation and the termination of therapy.
Results. The demographic data did not differ between the groups. Mean serum creatinine (171.5 vs 282.9 mmol L-1, p<0.05), blood lactate (1.8 vs 3.5 mmol L-1, p<0.05), and potassium concentrations (3.9 mmol L-1 vs 4.5 mmol L-1, p<0.05) were significantly higher in those patients who died. Mean SOFA scores were similar in both groups before the start of treatment, but were increased significantly at the end of therapy in the patients who died (7.0 vs 15.0, p<0.05). The concentrations of CRP, and WBC counts were similar in both groups.
Conclusions. We concluded that CVVH can be instituted in cases of ARF, regardless of age or condition of patients. Early institution of CVVH was effective and resulted in normalization of renal function and biochemical parameters.
Continuous veno-venous haemofiltration (CVVH) is a recognized and recommended method for continuous renal replacement therapy (CRRT) in ITU settings. It is an element of supportive treatment included in the guidelines for treatment of severe sepsis, septic shock and acute renal failure in haemodynamically unstable patients and those with acute renal failure who cannot undergo intermittent dialysis therapy [1, 2, 3]. CVVH is particularly indicated for muscle damage and crushing, cerebral oedema, acute hepatic failure with resultant cerebral oedema, congestive heart failure or parenteral feeding without limiting the kinds of nutrients at accompanying renal failure [4, 5, 6, 7, 8].
Once renal replacement therapy, which is technically advanced and expensive, is instituted some measurable effects are expected. Therefore, the aim of the present study was to evaluate the effects of haemofiltration on the clinical symptoms and selected laboratory parameters in patients treated in ITUs.
Retrospective analysis involved medical records of 480 patients treated in the Department of Anaesthesiology and Intensive Therapy, the multi-profile Upper Silesian Medical Centre between 01.09.2008-31.12.2009, of whom 22 patients underwent continuous veno-venous haemofiltration. The therapy was instituted in all patients with acute renal failure defined according to the RIFLE criteria (Risk, Injury, Failure, Loss, End-stage Renal Disease) (Table 1) .
In addition to the RIFLE inclusion criteria, at least one of the following indications for CVVH was considered:
- serum concentration of electrolytes, potassium, in particular (>5.5 mmol L-1 and its increase in time);
- metabolic acidosis resistant to traditional methods of treatment: supply of 8.4% NaHCO3 in the dose corresponding to deficiency of free bases and ventilatory compensation;
- serum lactate concentration (>2.2 mmol L-1);
- vascular bed filling with central venous pressure (CVP) considered (>12 mm Hg);
- diagnosis of systemic inflammatory response syndrome (SIRS).
Veno-venous haemofiltration was administered using the PrismaFlex system (Gambro, Sweden). The dialysis catheters used were 11 F (Gambro, Germany) and 12 F (Balton, Poland) whose length depended on the place of vascular access (20 cm − femoral, 17.5 cm – subclavicular and left jugular and 15 cm – jugular and right subclavicular access). The polyacrylonitrile filter ST 100 AN 69 (Gambro, Sweden) was used. The Dialisan BG2D fluids (Gambro, Italy) were applied whose electrolyte composition was corrected depending on baseline conditions of patients adjusting it to the expected potassium concentration in serum. On day 1 of treatment, the substitute dose ranged between 35 − 70 mL kg-1 h-1. During the next days, the dose was maintained at 35 mL kg-1 h-1. The initial blood pump rotations were 250-300 mL h-1, and were corrected according to the condition and efficiency of the filter and dialysis access. The initial distribution of substitute supply was 30% in predilution and 70% in postdilution. Ultrafiltration (UF) w
as determined according to patient’s diuresis and baseline vascular bed filling. In cases of anuria or oliguria, UF was initially determined as 1 mL kg-1 h-1 and corrected according to present vascular bed filling and daily fluid balance. During therapy, continuous anticoagulation with non-fractionated heparin was used to protect the filter under the control of indexed time of activated partial thromboplastin time (APTT) to achieve the value between 2.5 − 3.5 (reference value 0.84 − 1.16).
The patients were allocated into two groups: 1 − those with haemofiltration completed due to improvement and lack of indications for further renal replacement therapy, and 2 − patients who died during haemofiltration.
The study groups were evaluated according to age, gender, time from ITU admission and institution of renal replacement therapy, primary disease which caused renal failure, and duration of renal replacement therapy. Moreover, markers of haemofiltration efficacy were determined, including concentration of creatinine (daily), potassium (at least once a day), lactates (every other day), arterial blood pH (at least once a day), inflammatory markers − WBC (at least once a day), CRP (every other day) and effects of renal replacement therapy on clinical condition of patients according to the Sequential Organ Failure Assessment (SOFA).
The results were statistically analysed. The values were presented as –x±SD for quantitative variables of normal distribution and M and interquartile range (Q1; Q3) for variables with non-normal distribution. The types of distribution were verified using the Shapiro-Wilk test. For qualitative variables, their frequency of occurrence was given. The significance of differences between groups was evaluated using the Student’s t test with Yates correction or ANOVA. P ≤0.05 was considered statistically significant.
CVVH was used in 22 patients. In five of them CVVH was instituted in stage “R”, in another 5 in stage “I” and in 12 in stage “F” according to RIFLE. Eighteen patients were oliguric and 4 anuric. In these cases, the time from the decision to institution of CVVH did not exceed 6 h. Six patients were excluded from the study population because they died within 12 h from the onset of renal replacement therapy. Further analysis involved treatment of 16 patients: 5 in group 1 and 11 in group 2.
The mean age was 64.3±11.68 years; in the group with completed haemofiltration − 57.8±15.27 and in the group treated unsuccessfully – 67.27±9.7. No significant gender-group differences were observed.
On average, CVVH was instituted on day 2 after ITU admission, which was comparable in both groups.
In group 2, the commonest cause of acute renal failure was retroperitoneal haematoma due to ruptured aneurysm of the abdominal aorta and sepsis during peritonitis. In group 1, none of the primary injury predominated (Table 2).
In group 1, haemofiltration was used for 8 days (Q1=7.0, Q3=9.0) whereas in group 2 for 3 days (Q1=2.0, Q3=8.0); the duration of therapy did not differ significantly between the groups.
Serum creatinine concentration on institution of haemofiltration did not differ between the study groups. During the further days maximum creatinine concentration was significantly higher in group 2 whereas minimum creatinine concentration – significantly lower in group 1 (Table 3).
The serum concentration of potassium on institution of renal replacement therapy, during CVVH and after its completion, was significantly higher in group 2 (Table 3).
In all patients, metabolic acidosis was found on day 1 of treatment. On institution of therapy, pH was similar in both groups. Its value during therapy was significantly higher in group 1 (Table 3).
The concentration of lactates on CVVH institution did not differ significantly between the groups. In non-survivors significantly higher lactate concentrations were recorded by the end of therapy (Table 3).
CRP concentrations and WBC counts on the onset of CVVH and their changes during therapy were comparable in the study groups.
There were no intergroup differences in severity of clinical conditions on CVVH institution − the SOFA score of 14-15. During therapy, the score did not change in group 2 whereas in group 1 was significantly lower, i.e. 7 (p<0.0004).
Haemofiltration was applied in patients with various initial diseases and of different ages; therefore, the groups were not clinically homogenous.
It was demonstrated that the initial clinical conditions of patients did not have significant effects on the course of treatment as both groups had comparable SOFA scores on the CVVH institution, thus the risk of death was also similar . In survivors, the SOFA scores markedly decreased during the first days of renal replacement therapy, which resulted from a decrease in creatinine and urea concentration, arterial blood pH normalization, reduced doses of catecholamines or improved respiratory efficiency (increased PaO2/FIO2), which are the components of SOFA score. Our findings were consistent with the data reported by other authors [10, 11, 12].
Due to the complexity of therapy in the ITU setting, haemofiltration cannot be regarded as the only element determining the successful treatment; however, certain haemodynamic stabilization of patients visible in lower SOFA scores was evidently noticeable in both groups during the first day of therapy. This was likely to be associated with a well known yet controversial phenomenon of removal and adsorption of inflammation mediators on the haemofilter membrane, better control of vascular bed filling, not to mention normalization of arterial blood pH . Unfortunately, in non-survivors, after the initial stabilization and transient improvement, the general condition deteriorated, which resulted in higher SOFA scores and destabilization of biochemical parameters.
The time between ITU admission and institution of renal replacement therapy did not determine the survival. However, it should be emphasized that attempts were made to institute haemofiltration as fast as possible during acute renal injury . If feasible, the therapy was started during „R” or „I” stage of injury risk, which was not always possible since some patients were in stage „F” of renal failure (RIFLE) on ITU admission. According to the reports, this was associated with higher risk of therapy failure .
Moreover, prognosis and success of therapy depended markedly on the stage of septic shock manifesting itself as the maximum lactate concentrations during therapy and minimum pH of arterial blood. Noteworthy, in both groups during the first days after the onset of haemofiltration, pH normalized which improved homeostasis and provided time for more effective causal treatment .
Furthermore, an important sequel of CVVH therapy was normalization of concentration of potassium ions in blood, which eliminated the risk of hyperkalaemia-related life-threatening consequences. Haemofiltration started early, before the development of marked water-electrolyte abnormalities, resulted in significantly better outcomes, according to the AEIOU criteria of acidosis for renal replacement therapy .
In our centre, continuous methods are used only in ITU patients as opposed to intermittent techniques used in dialysis centres. In the latter case, treatment outcomes seem to be better and mortality lower (51%). It is of importance, however, that veno-venous haemofiltration in the ITU settings is used in the most highly affected patients, whose general conditions, and hence necessary continuous and advanced monitoring of vital functions and therapy methods, limit the management options.
1. Veno-venous haemofiltration is an effective therapy of acute renal failure; the age of patients and severity of diseases do not limit its use.
2. Veno-venous haemofiltration instituted early is an effective method to stabilise vital functions and normalise renal parameters.
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