In NICUs, use of dialysis in premature infants who are susceptible to AKI because of their immaturity or exposure to infection and toxins is gradually increasing [4, 5, 17]. However, to date, there is no guideline-based evidence regarding the indications and methods of RRT for premature infants. If renal failure does not resolve despite medical treatment, the timing and method of dialysis are selected on the basis of the decision of the primary care physician [8, 20, 21]. As a result, the prognosis of premature infants with AKI treated with RRT is poor. ELBW infants in particular are at very high risk for AKI, but few studies have suggested criteria for successful dialysis in ELBW infants with AKI. Although a recent study reported performance of APD in three ELBW infants, all infants received different types of peritoneal catheters and different technical methods were used [14]. Mortality of ELBW patients is generally high because these patients' organs are immature and failure of other organs often occurs [22].
Despite reports of application of hemodialysis (HD) in infants [23], HD may not be the neonatal treatment of choice for the following reasons: (1) the priming volumes for hemoperfusion filters are too large, requiring a minimum of 35 mL, making maintenance of the circulatory dynamics of premature infants difficult; (2) hemoperfusion filters require heparin to maintain patency; and (3) thrombocytopenia is a common complication of hemoperfusion. These factors can increase the risk of intracranial hemorrhage in neonates [20, 24]. In ELBW infants, who have unstable blood pressure and in whom obtaining vascular access is difficult, HD is hard to apply effectively.
Over the years, PD has become an effective and increasingly popular alternative to HD for the management of critically ill neonates, including premature infants [9, 25]. APD is relatively safe, technically simple, and cost-effective. It can also be applied in hemodynamically unstable premature infants [2, 8, 12, 25]. Catheter design, implantation site, and system configuration used to perform dialysis determine the effectiveness of APD in premature infants. However, the most common difficulty in APD is the introduction of a suitable peritoneal catheter for these patients. Obtaining catheter access for APD is more difficult in ELBW infants than in older neonates because of their small size and inelastic abdominal wall.
Permanent PD catheters (e.g., Tenckhoff catheters) with cuffs are very rigid and too long for the small intra-abdominal cavities of infants. They need to be tunneled under the skin. However, in ELBW infants, APD catheters can be inserted directly through the abdominal wall, without tunneling. Temporary PD catheters are generally inserted along with IV catheters or commercially available peritoneal catheters [22]. Other alternatives are feeding tubes, suction catheters, neonatal chest drains, and Foley catheters [26-28]. In our study, although APD catheters were inserted in eight of the 12 patients, IV catheters (e.g., ARROW® CVC and venous umbilical catheters) were inserted initially in another four patients because of their low body weight. When using IV catheters, we manually created some side holes during the procedure. We expected these holes to have better permeability. Although these holes could have rough edges, which may cause bowel perforation or intraperitoneal hemorrhage, no such complications were observed in our study. PD worked effectively in two ELBW infants with smaller-sized catheters.
Complications associated with APD in premature infants include mechanical dysfunction, such as dialysate leakage and catheter obstruction requiring revision or reinsertion, intraperitoneal hemorrhage, and bowel perforation [17, 20, 29]. Peritoneal fluid leakage around the APD catheter and along the tunnel is a serious problem that can increase the risk of bacterial and fungal peritonitis [21, 30]. In this study, the complications observed in relation to APD were caused mainly by catheter-related dialysate leakage, which was resolved after adjustment of the dwell volume or reinsertion of the catheter on the other side. In a previous study, a tissue adhesive, i.e., commercially available fibrin glue, was used at the insertion site [29]. Therefore, selection of an optimal catheter for APD is very important to minimize complications associated with APD access. In our study, the ability to discontinue APD in two patients was due to low leakage of the APD catheter, which affected net UF due to efficient APD action. A severe complication of APD is peritonitis, but only one patient in this study developed peritonitis. The use of prophylactic antibiotics should be carefully considered taking into account infection prevention versus generation of antibiotic-resistant bacteria [25, 28]. The efficacy of APD in ELBW infants is affected by many factors. In ELBW infants with hypotension, peripheral perfusion is insufficient for adequate exchange. If they develop sepsis, which increases vessel permeability, rapid solute removal and UF capacity reduction with gradient loss may occur [31].
Increasing the number of exchanges, administering large volumes of dialysate, or adjusting the concentration of glucose in dialysis fluids may help improve dialysis efficiency [32]. Although the number of exchanges may vary, approximately 24 exchanges per day are employed for APD. The number of exchanges is determined by the amount of fluid and solute removal required. A total of 20-40 cycles can be used; further, the procedure can be continued until the desired effect is obtained [32, 33]. The size of the peritoneal cavity, weight of the infant, presence of pulmonary or other diseases, and degree of uremic toxicity may influence the exchange volume [12, 34]. Additionally, it is rational to initiate APD using 2.5% dialysate solution to achieve better UF [12, 34]. Estimation of the peritoneal equilibration rate is necessary for optimal dialysis; however, practically frequent blood and dialysis fluid sampling is risky in ELBW infants. In our study, APD was started at the rate of 10 mL/kg, which was increased to 20-30 mL/kg at 60-120 min/cycle continuing for 24 hours.
In our study, the mortality rate of the ELBW infants treated with APD was high at 91.7%. In addition, most of the patients had findings compatible with disseminated intravascular coagulation features. In a previous study, the mortality rate was 79% in ELBW infants treated with APD; they were assumed to have died from underlying medical conditions and multi-organ failure rather than renal failure [20, 25]. In the current study, five ELBW infants had accompanying congenital heart disease and twin-to-twin transfusion. Initiation of dialysis may decrease urine output and intravascular volume, making negative renal recovery an issue. This could aggravate underlying diseases, including congenital heart disease, which would increase the mortality rate of ELBW infants. However, a strength of this study is that it provides data on the effects of dialysis in ELBW infants with congenital heart disease or twin-to-twin transfusion; these effects have previously been monitored in only a few studies.
Our study had some limitations. First, it was a retrospective study of a relatively small number of infants conducted at a single center; thus, the findings might not be generalizable to larger populations. Second, our data do not indicate whether the nutritional intake of ELBW infants causes high morbidity and mortality rates in maintenance dialysis. Lastly, we did not include premature infants with contraindications for APD, such as NEC, severe respiratory failure, and hemorrhagic tendency. Intrusion of the peritoneal cavity or placement of multiple abdominal drains may occur in infants with these contraindications. The available data from this and previous studies on treating ELBW infants with APD or HD for AKI suggest that alternatives to these techniques are required for the treatment of premature infants with AKI.