Utilization of Peritoneal Dialysis in the Acute Setting

Peritoneal Dialysis in Acute Renal Failure (Arf)

There is no consensus in the literature on the best method or ideal dialysis dose in ARF, although studies have reported that continuous methods providing the highest possible dialysis dose are beneficial in hypercatabolic patients and those with cardiovascular instability (1,2). The nephrologist's experience with the procedure and the availability of different dialysis modalities play an important role in this choice.

In a recent study involving 54 nephrology centers distributed over five continents, Uchino et al. (3) reported that continuous venovenous dialysis techniques were the major methods used in patients with ARF in almost 80% of services, while PD was used in 3.2% of these centers and intermittent hemodialysis (HD) in 16.8%. In Latin America, particularly in Brazil, PD was used in 23% of patients with ARF and in Europe in 21% (4). There are no studies reporting survival rate differences for patients submitted to these methods.

Peritoneal dialysis for ARF still constitutes the mainstay of therapy in many developing countries due to its availability and ease of administration (5). Despite its decreasing use, PD should not be discarded as an unworthy therapeutic option for patients with ARF, since this modality offers several advantages over HD, such as its technical simplicity, no extracorporeal circuit, and no bleeding risk. Because of its gradual and continuous nature, it leads to solute and liquid removal with excellent cardiovascular tolerance, and therefore less hemodynamic instability, reducing both kidney aggression by ischemia and risk of hydroelectrolytic imbalance (6). It has been indicated mainly for children, patients with ARF and cardiovascular instability, coagulopathies, and difficult vascular access (7,8).

There is no consensus for satisfactory urea levels in ARF. Katirtzoglou et al. (9) reported blood urea nitrogen (BUN) levels below 100 mg/dL, which were considered satisfactory at that time for ARF patients on continuous peritoneal dialysis (CPD). Mehta and Letteri (10) reported that intermittent PD was not adequate for treating ARF patients, as BUN levels remained higher than 75 mg/dL. They reported that the peritoneal membrane presents low solute clearance capability, which does not agree with other studies reporting efficient fluid removal and metabolic control in patients in whom CPD therapy was prescribed (11,12). Phu et al. (13) reported that CPD failed to satisfactorily control BUN and creatinine levels compared to continuous venovenous hemofiltration, the first group having a significantly higher mortality rate (47% vs 15%). However, a rigid peritoneal catheter was used, exchanges were manually performed, and the dwell time was too short, leading to inadequate solute clearance and dialysis efficiency. Notably, the same authors had previously published a study showing a significant reduction in ARF patient mortality associated with malaria; they also concluded that PD could be an alternative for intermittent HD (12). Chitalia et al. (14) elegantly demonstrated that tidal and CPD are adequate methods of maintaining BUN levels at about 65 mg/dL in mild and moderate hypercatabolic ARF patients in developing countries. In their prospective and randomized study, 87 patients received 236 dialysis sessions by flexible catheter and automated PD with a cycler. Peritoneal dialysis was successful at the dialysis dose in these patients with a delivered Kt/V of 2.4 for tidal and 1.8 for CPD, both meeting National Kidney Foundation adequacy standards. Recently, Gabriel et al. (15), in a prospective study with 30 ARF patients who received 236 sessions of CPD, gave encouraging results for metabolic, electrolytic, and acid–base control. They showed that high doses and CPD by flexible catheter and cycler was an effective treatment for ARF; providing high solute removal in this study provided a sufficient dialysis dose, with higher values than described in recent literature.

Peritoneal dialysis does have some limitations, such as the need for an intact peritoneal cavity. Also, recent abdominal surgery and, to some extent, the presence of adynamic ileum and peritoneal fibrosis or adherences are other contraindications (7,8). As for limitations in ARF patients, PD is less effective than HD in treating emergency situations such as acute pulmonary edema, poisoning, and drug intoxication.

Infectious, mechanical, and metabolic complications are the major problems with PD in ARF. Previous studies have reported a 12% – 25% incidence of peritonitis, with a predominance of gram-positive etiological agents, as well as fungi in debilitated patients undergoing antibiotic therapies (16,17). The increasing use of automated dialysis via flexible catheter has led to a reduction in peritonitis frequency, as peritonitis is more often associated with rigid catheters and manual changes (5).

Regarding mechanical complications, studies have shown that dialysate overflow occurs in fewer than 10% of cases, due to immediate PD use just after catheter insertion (15,18). There is controversy about abdominal distension leading to reduced diaphragm mobilization and consequently about pulmonary compliance (19).

Protein losses may play an important role in PD, mainly during peritonitis, since they can exacerbate conditions in undernourished critical patients. Blumenkrantz et al. (20) measured protein losses and identified influencing factors during intermittent PD and CPD. They showed that total weekly protein losses were around 45 g in intermittent PD and 62 g in CPD, and that albumin accounted for approximately half of this loss. Despite this depletion, drops in plasma albumin and total protein levels were not observed. There was no significant variation in each individual loss, but large variability among individuals was seen. Peritonitis was the only factor influencing these losses. Similar results were shown by Gabriel et al. (15), where there was no significant difference between median plasma albumin values obtained before and during CPD sessions (median 2.6 g/dL), despite considerable losses in protein (median 21.7 g/day). The authors concluded that dialysate protein loss, although significant, was not a limiting factor for using the technique. In these situations, it is necessary to increase patient protein ingestion, which should be 1.5 g/kg/day (21,22).

Hyperglycemia is another metabolic complication resulting from PD that can cause diabetic disorders and therefore requires regulated use of insulin via continuous infusion pump to control glycemia (14,21).

Finally, there are controversies about the influence of PD on respiratory mechanics. Bazari (23) reported that PD impairs diaphragm mobilization because of increased intra-abdominal pressure. As a result, pulmonary compliance and ventilation are impaired. Venous return is also reduced, leading to hypotension and consequently to organ and tissue hypoperfusion, which favors acidosis. However, Epstein et al. (24) showed that, although dialysate reduces pulmonary volume, characteristics of vital capacity and expiratory volume remain unaltered. They concluded that PD is rarely associated with ventilatory impairment in patients without pulmonary pathologies.

These findings provide evidence that adequate prescription of CPD leads to outcomes comparable with other dialysis methods. It is therefore an important therapeutic alternative to continuous venovenous therapies and daily HD, especially in places where these methods are not available or are impractical.

Peritoneal Dialysis in Congestive Heart Failure (Chf)

Peritoneal dialysis can also be used to maintain volemic control in patients with CHF without ESRD. Patients with rapidly worsening cardiac function can present renal vasoconstriction and resistance to diuretics, with accumulation of liquids. In these situations, PD may improve cardiac output due to the Frank–Starling mechanism, an increased left ventricular diastolic inflow and an improvement in lung compliance after removal of the excess fluid (25-27). Peritoneal dialysis can reduce plasmatic volume, correct hyponatremia, and improve both the response to diuretics and glomerular filtration (28,29). For the same reasons, PD may also be useful in chronic CHF treatment without ESRD. In the literature there are diverse studies that describe the favorable evolution of patients with CHF submitted to PD (30-32). The principal advantage of this therapy is the slow removal of liquids with good patient tolerance and reduced costs, which becomes an attractive therapeutic alternative for developing countries. At the present date, there have been no comparative studies of dialysis modalities in CHF treatment, or any studies that demonstrate changes in the prognosis of patients submitted to this dialysis modality.

Peritoneal Dialysis as a “Bridge” in Patients Submitted to Chronic Hd

Patients with ESRD that initiate dialysis treatment through PD present lower risk of death than those submitted to HD in the first 30 months of treatment (33). This finding may be associated with better preservation of residual renal function in patients in PD and with the utilization of central venous catheters as a form of vascular access in HD. Studies show that patients with a provisory vascular access present risks of bacteremia and mortality greater than those with an arteriovenous fistula (34,35). These catheters may present a biofilm covering on their walls, with bacteria in their interiors, facilitating the occurrence of infections such as endocarditis and sepsis (36). Despite that, recent data show that, in European countries, Canada, and the United States, this is the principal venous access in patients that initiate HD (37).

Fernández–Cean et al. (38) showed that PD can be utilized as a “bridge” in patients submitted to HD with provisory vascular access that presented infectious endocarditis. Comparing two groups with similar clinical characteristics, they verified that the mortality in patients submitted to a new central catheter implant was 55.5%, while in those submitted to transitory PD it was only 8.3%. In this manner, PD utilized as a transitory procedure until the elaboration and maturation of a definitive vascular access, as proposed by Hakim and Himmelfarb (39), can improve the survival of patients with ESRD that will be submitted to HD.

Other situations in which PD can be utilized include control of hyperthermia and treatment of necrohemorrhagic pancreatitis when abdominal cavity washing is beneficial. However, new studies must be accomplished so that the benefits of this treatment may become evident.