AKI in intensive care over the past decade has seen a proliferation of literature and has been widely treated by international (1) and national guidelines (2). It is showed less interest the treatment of AKI in patients not requiring Intensive Care Unit admission, often hospitalized in Nephrology Unit. Over time such type of patients has changed. These are often critically ill with many comorbidities and with hemodynamic instability, not easily managed with the standard intermittent dialysis treatment. The intradialytic management of these patients frequently is complex and requires a very high level nurse- patient relationship. It is conceivable that even the AKI in Nephrology hospitalization may benefit from treatments slow with low efficiency, whether continuous or intermittent dailies lenses. For critically ill patients, for dialysis efficiency purposes, guidelines (2) detect that it is highly complex to define the correct dialysis dose to prescribe, because often the prescribed dose is less than that obtained (3, 4, 5). Seems not defined, in case of hybrid techniques, slow intermittent, what is the dialysis efficiency index to be applied.
In our Center from about 5 years is being implemented a new protocol for the treatment of AKI who, aimed at obtaining a Kt/V urea at least equal to that of daily dialysis for patients with MRC, was easy to implement and was of low impact to the nursing staff. With this Protocol were treated about 500 pt.
In this study we report the clinical results obtained in 100 consecutive patients referred to our Nephrology Unit from 1/1/2014 requiring dialytic treatment for AKI.
One hundred consecutive patients referred to our Nephrology Unit from 1/1/2014 requiring dialytic treatment for AKI were analyzed. Dialysis Protocol provides an intermittent slow low efficiency treatment, called SLE-HDF (Sustained Low Efficiency Hemo-Dia-Filtration). The dialysis was initiated for oligo-anuria resistant to medical therapy, for electrolyte abnormalities at risk of death or severe hyperhydration resistant to diuretics. Basic dialysis scheme provided for a duration of 10 hours, with 1.5 L/h of dialysate for a patient to 70-75 kg. Half of the dialysate was used in convention in post and half in diffusion, for a total of 15 L for session. To monitor where there was a pre-dilution, this was reduced to only 100 cc/hr. In case of higher weight patients the dialysate volume was 20 L up to 85 Kg and 25 over 85 Kg (Tab. I). Five patients with AKI and lactic acidosis from metformin were excluded because had been treated with CVVHDF. The replacement liquid had the following composition: Calcium 1,75 mmol/l, magnesium 0,5 mmol/l, sodium 140 mmol/l, chloride 111,5 mmol/l, lactate 3, Bicarbonate 32, potassium 2 or 4, Glucose 6.1. The K content was modified, with the range 2 to 4 mEq / L, based on the values of serum potassium. We have chosen the SLE-HDF instead of CVVHDF essentially for not wanting to engage the nursing staff during the night. It has been excluded SLED not being available in patient nephrology the osmotic water. Dialyzers were used in semi-permeable hollow fibers high biocompatibility. As an anticoagulant was used in grade unfractionated heparin in continuous infusion and low molecular weight heparin bolus in case of signs of heparin-induced thrombocytopenia. The treatment was done in Nephrology Unit, with continuous monitoring of body weight, heart rate, blood pressure and oxygen saturation. The preparation of the dialysis monitor and the in -out patient was dialysis staff's task. The general assistance was instead by the staff of Nephrology, as well as interventions for the detection or alarm off. Only in case of special interventions (repeated alarms, malfunction of CVC circuit clotting) had requested the intervention of the dialysis technician. The dialysis efficiency index was considered a daily 0.4 Kt/V urea as suggested by several authors for daily HD or frequent (6 - 8). In all patients it was evaluated the UKT/V at least for a dialysis session, according to the formula: Urea D/P x volume dialysate x 0.58 x BW where D/P is the Dialysate/Plasma ratio and BW is body weight in kg. The value of urea serum used was the average of the values at the beginning and end of dialysis, while the value of the dialysate urea was evaluated all over the dialysate. The SLE-HDF was suspended when, in the presence of an adequate urine output, biochemical profile showed no substantial changes after two days of temporary discontinuation of treatment. For patients started on chronic dialysis, the resolution of acute cases which had resulted in the AKI, the awareness of an impossible recovery of renal function induced suspension of SLE-HDF and the initiation of chronic dialysis or hemodialysis or dialysis peritoneal. As vascular access was used in the first instance the CVC acute, varying in length from 19 to 24 cm, in the right femoral vein. The right internal jugular vein was first choice in case of femoral or not usable and in case of potential candidates to renal transplant patients. Catheterization of the central veins was performed by the team nephrology in eco-driving. Of each patient were detected the cause of AKI and comorbidities. In 5 patients anuric, who performed the dialysis treatment for a minimum of five days, we monitored the serum values of urea, creatinine, K, Ca, P and bicarbonate. Endpoints were considered 3, renal functional recovery, start to chronic dialysis and exitus.
Fig.1 shows the case histories of our patients, who were 45 females and 55 males, mean age 79.4 + 11 aa. The causes of AKI were: heart failure 41%, electrolyte imbalance 31%, 7% post-renal, 6% hepatorenal syndrome, sepsis 4%, 11% other. Among the causes of AKI heart failure, electrolyte imbalances and IRA on IRC were the most frequent. The most represented comorbidities were heart disease (63%), diabetes (50%), COPD (38%), age> 85 years old (31%), cancer (23%), liver disease (16%), hypotension applicant amines (15%), (10%) (Fig. 2). The 38% of patients shoved 3 comorbidity or more (fig.3). The body weight at the start of dialysis treatment was 74 + 18 kg. The mean values of urea and creatinine at the time the treatment was 201 + 83 mg/dl and 5.4 + 2.8 mg/dl respectively (fig.4). The 65% of patients had a minor urine output of 500 ml / 24 hours, 16% between 500 and 1000 ml/24 hours when starting the dialysis (Fig.5). In 100 patients they were performed 512 treatments, on average 12.5 + 3.7 per patient (minimum 1 maximum 19 sessions). The mean of the UKT/V was 0.4 + 0.05 per session. Regarding clinical outcomes have been 43 deaths and 57 resigned, 43 of which for improvement of AKI; 14 patients have taken over renal function and started on chronic dialysis. Many patients achieved a considerable removal of liquids, with an important weight decrease that in many cases was more than 10 kg (fig. 6). In Fig. 7 the mean values of urea, creatinine, Ca, P, and HCO3 of 5 anuric patients in 5 days of SHE-HDF treatment are plotted; the data show the purifying effectiveness of the treatment.
It seems clear that the our dialytic protocol was efficient regarding clinical outcomes and control of metabolic panel. In fact, 57% of patients have shown an improvement for 57 % of the general conditions (47 % of them with recovery of renal function). This result may be considered satisfactory considering that 48% of the patients had three or more comorbidities, 41 % had heart failure, 23% were suffering from cancer, 6 patients had hepatorenal syndrome and 31% were over 85 years. About the dialysis efficiency, the weakly UKt/V was about 2.8, comparable to Ukt/V obtained in various experiences with the daily dialysis. The daily dialysis was carried out 6 days a week and not 7, with very short dialysis sessions, on average 2 hours (6, 7, 8). To equate the same Kt/V obtained by a short dialysis to one with a long dialysis probably tends to underestimate the second. On the other hand, the Working Group on KDIGO of the Canadian Society of Nephrology (9) remarks that, in the absence of evidence of high levels of quality, it is possible to consider appropriate the same criteria currently used for chronic dialysis patients. The target of clearance and dialysis prescription based on urea can also be used in critically patients undergoing RRT for AKI to maximize the treatment and identify the minimum adequate dialysis dose (9). Regarding the volume of dialysate, the one used in our protocol appears not in line with as suggested for CRRT (1, 2). In fact, though partly based to the minimum volumes of 20 ml/kg/hr, that in 24 hours for a patient of 70 kg is equivalent to 33.6 L, total volume used by us is less than half. There is no question that this aspect, in addition to saving solutions, implies a smaller number of operator interventions (10). Indeed, whereas many monitors have the possibility to connect 4 sacs, with 20 liters can treat most patients without the need of intervention for the exchange of the bag. It is possible that in patients hypercatabolic a weekly UKT/V of 2.8 may be inadequate; in this case, by increasing the volume of 5 l of dialysate are unable to significantly improve the UKT/V (Tab.I). On the other hand, an important recommendation is the constant revaluation of the treatment in the individual patient, increasing the dose prescribed in case of actual need without exceeding a priori the minimum requirement, how recommended by canadian society of nephrology (9). In no case, in our experience we had to increase the volume of dialysate for inadequate control of metabolic and electrolyte panel. On the other hand, some randomized studies, evaluating the importance of a high versus a low efficiency dialysis, showed no difference in mortality (11, 12). In the evaluation of the efficiency dialysis, in comparison between the SLE-HDF and CRRT, it should be noted that while in these last there is uncertainty, because of interruptions and reductions in system efficiency, in SLE-HDF as in all intermittent treatment, dialysis dose typically is certain. Another element to consider, regarding the use of significantly lower volumes than recommended in the literature, is the potential loss of micronutrients during treatment with CRRT, especially when we use high volumes. It’s known that the continuous treatments often lead severe ipofosfatemie and ipokaliemie (13,14). Some authors have stressed the importance of risk malnutrition in patients with AKI in substitution treatment. This risk for poor nutrition or inadequate is aggravated by the loss of amino acids and other nutrients that occurs in the course of slow treatments such as SLED (15,16) or even more in the course of high-flow continuous treatment (14). It’s conceivable that the treatment at low volumes of our protocol can induce minor leakage of amino acids and nutrients normally.
Our protocol dialysis of "SLE-HDF" 15 liters in 10 hours, has moved the efficiency of dialysis by target volumes, intended as the amount of dialysate pro kg/hour, to the concept of dialysis adequacy always used for chronic dialysis as well as supported by the Canadian Society of Nephrology (9). In addition, a treatment of 10 hours often has the certainty of the dialysis dose, compared to a treatment of CRRT, in which, for a decrease of the rendering of dialyzer or to interruptions of the session, there may be a reduction in efficiency. The reduction of dialysate volume to less than half of that established for CRRT, permit to obtain an adequate weekly urea Kt/V, reducing the cost of treatment with lower commitment to the nursing staff. The low volume of dialysate could also reduce the problems associated with the loss of micronutrients and amino acids, and therefore have a positive impact on the nutritional status of patients.
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