Stability of Continuous Renal Replacement Therapy Solutions After Phosphate Addition: An Experimental Study

Effect of Phoxilium on prognostic predictors in patients undergoing continuous venovenous hemodiafiltration

Background

Phosphorus-containing dialysis solution is used to prevent hypophosphatemia in patients undergoing continuous venovenous hemodiafiltration (CVVHDF). This study evaluated the effect of phosphorus-containing dialysis solution on mortality in patients undergoing CVVHDF based on changes in phosphorus and red cell distribution width-coefficient of variation (RDW-CV) levels.

Methods

We included 272 patients with acute kidney injury (AKI) who underwent CVVHDF at the medical intensive care unit from 2017 to 2019 and classified them according to Phoxilium (Baxter Healthcare Ltd.), as a phosphorus-containing dialysis solution, use within 48 hours after CVVHDF initiation. Clinical data were collected at baseline and 48 hours after CVVHDF initiation. The primary outcome was all-cause mortality during the follow-up period.

Results

The non-Phoxilium (NP) group had higher phosphorus and lower RDW-CV levels than the Phoxilium (P) group (phosphorus, 7.3 ± 4.3 vs. 5.0 ± 2.8 mg/dL; RDW-CV, 14.6 ± 1.9 vs. 15.7 ± 2.6%; all p < 0.001). In the multivariable Cox proportional hazard regression of the NP group, an increase in phosphorus and RDW-CV at 48 hours of CVVHDF was associated with mortality (delta phosphorus: median, >0 mg/dL vs. <-2.0 mg/dL; hazard ratio [HR], 8.62; 95% confidence interval [CI], 2.10-35.32; p = 0.003/delta RDW-CV: median, >0% vs. <-0.2%; HR, 4.34; 95% CI, 1.49-13.18; p = 0.008). Meanwhile, in the P group, an increase in delta RDW-CV was associated with mortality (delta RDW-CV: >0% vs. >-0.2% and <0%; HR, 2.65; 95% CI, 1.12-6.24; p = 0.03), while an increase in delta phosphorus was not.

Conclusion

In patients with AKI undergoing CVVHDF, the risk factors for all-cause mortality differed according to the initial phosphorus levels and use of Phoxilium.

Hypophosphatemia in critically ill patients with acute kidney injury on renal replacement therapies

Hypophosphatemia is a common but often underestimated electrolyte derangement among intensive care unit (ICU) patients. Low phosphate levels can lead to cellular dysfunction with potentially relevant clinical manifestations (e.g., muscle weakness, respiratory failure, lethargy, confusion, arrhythmias). In critically ill patients with severe acute kidney injury (AKI) renal replacement therapies (RRTs) represent a well-known risk factor for hypophosphatemia, especially if the most intensive and prolonged modalities of RRT, such as continuous RRT or prolonged intermittent RRT, are used. Currently, no evidence-based specific guidelines are available for the treatment of hypophosphatemia in the critically ill; however, considering the potentially negative impact of hypophosphatemia on morbidity and mortality, strategies aimed at reducing its incidence and severity should be timely implemented in the ICUs. In the clinical setting of critically ill patients on RRT, the most appropriate strategy could be to anticipate the onset of RRT-related hypophosphatemia by implementing the use of phosphate-containing solutions for RRT through specifically designed protocols. The present review is aimed at summarizing the most relevant evidence concerning epidemiology, prognostic impact, prevention and treatment of hypophosphatemia in critically ill patients with AKI on RRT, with a specific focus on RRT-induced hypophosphatemia.

Phosphate supplementation for hypophosphatemia during continuous renal replacement therapy in adults

Background: Hypophosphatemia is common during continuous renal replacement therapy (CRRT) in critically ill patients and can cause generalized muscle weakness, prolonged respiratory failure, and myocardial dysfunction. This study aimed to investigate the efficacy and safety of adding phosphate to the dialysate and replacement solutions to treat hypophosphatemia occurring in intensive CRRT in critically ill patients.

Methods: We retrospectively analyzed 73 patients treated with intensive CRRT (effluent flow ≥35 ml/kg/hr) in the intensive care unit. The control group (group 1, n = 22) received no phosphate supplementation. The treatment groups received dialysate and replacement solution phosphate supplementation at 2.0 mmol/L (group 2, n = 26) or 3.0 mmol/L (group 3, n = 25).

Results: The CRRT-induced hypophosphatemia incidence was 59.0%. Correction of hypophosphatemia with phosphate supplementation changed the mean serum phosphorus levels to 1.24 ± 0.37 and 1.44 ± 0.31 mmol/L in groups 2 and 3, respectively (p = .02). The time required for correction was 1.65 ± 0.80 and 1.39 ± 1.43 days for groups 2 and 3, respectively and was significantly longer in group 2 (p = .02). After supplementation, hypophosphatemia, and hyperphosphatemia both occurred in 7% of group 2. Group 3 developed no hypophosphatemia, but 20% developed hyperphosphatemia. The serum phosphate levels in hyperphosphatemia cases returned to normal within 2.0 days (group 2) and 1.0 day (group 3) after stopping phosphate supplementation.

Conclusion: Phosphate supplementation effectively corrected CRRT-induced hypophosphatemia in critically ill patients with an acute kidney injury. The use of 2 mmol/L phosphate is appropriate in patients with CRRT-induced hypophosphatemia, but a different concentration could be required to prevent hypophosphatemia at the start of CRRT.

Prevention of hypophosphatemia during continuous renal replacement therapy-An overlooked problem

Hypophosphatemia is a common and potentially serious complication occurring during continuous renal replacement therapy (CRRT). Phosphate supplementation is required in the vast majority of patients undergoing CRRT, particularly beyond the first 48 hours. Supplementation can be provided either as a standalone oral or parenteral treatment or as an additive to CRRT solutions. Each approach has advantages and disadvantages, and clinicians must weigh the individual factors most relevant in their practice setting. Currently there are no consensus protocols for phosphate replacement in CRRT, and many centers replete phosphate in response to hypophosphatemia as opposed to pre-emptively. Repletion protocols have also been challenged in recent years by shortages in injectable phosphate solutions. More recently a commercially available phosphate-containing CRRT solution was approved in the United States, but there has been limited clinical experience with this product. In this review, we present recommendations for phosphate repletion in CRRT to prevent hypophosphatemia, and describe our experience using phosphate-containing CRRT solutions.

Phoxilium(®) reduces hypophosphataemia and magnesium supplementation during continuous renal replacement therapy

Background

Although associated with severe clinical complications, phosphate remains a neglected ion. Additionally, phosphate balance during continuous renal replacement therapy (CRRT) is complex and multifunctional. The present retrospective study investigated the effects of phosphate-containing CRRT fluid on phosphate homeostasis.

Methods

We retrospectively analysed 112 patients treated with CRRT at Skåne University Hospital, Sweden. The control group was treated with Hemosol^® B0 (no phosphate; n = 36) as dialysis and replacement fluid, while the study group received Phoxilium^® (phosphate; n = 76) as dialysis fluid and Hemosol^® B0 as replacement fluid.

Results

Hypophosphataemia (<0.7 mM) occurred in 15% of the treatment days in the control group compared with 7% in the study group (P = 0.027). Magnesium substitution was reduced by 40% in the study group (P < 0.001). No differences in acid–base parameters were detected between the groups.

Conclusions

In this larger cohort, we could confirm that Phoxilium^® reduced the episodes of hypophosphataemia during CRRT. A beneficial effect on magnesium balance could also be observed.

Applying lean principles to continuous renal replacement therapy processes

PURPOSE

The application of lean principles to continuous renal replacement therapy (CRRT) processes in an academic medical center is described.

SUMMARY

A manual audit over six consecutive weeks revealed that 133 5-L bags of CRRT solution were discarded after being dispensed from pharmacy but before clinical use. Lean principles were used to examine the workflow for CRRT preparation and develop and implement an intervention. An educational program was developed to encourage and enhance direct communication between nursing and pharmacy about changes in a patient's condition or CRRT order. It was through this education program that the reordering workflow shifted from nurses to pharmacy technicians. The primary outcome was the number of CRRT solution bags delivered in the preintervention and postintervention periods. Nurses and pharmacy technicians were surveyed to determine their satisfaction with the workflow change. After implementation of lean principles, the mean number of CRRT solution bags dispensed per day of CRRT decreased substantially. Respondents' overall satisfaction with the CRRT solution preparation process increased during the postintervention period, and the satisfaction scores for each individual component of the workflow after implementation of lean principles. The decreased solution waste resulted in projected annual cost savings exceeding $70,000 in product alone.

CONCLUSION

The use of lean principles to identify medication waste in the CRRT workflow and implementation of an intervention to shift the workload from intensive care unit nurses to pharmacy technicians led to reduced CRRT solution waste, improved efficiency of CRRT workflow, and increased satisfaction among staff.

Specialized nutritional support interventions in critically ill patients on renal replacement therapy

PURPOSE OF REVIEW

Optimal nutritional requirements and nutrient intake composition for patients with acute kidney injury remain a partially unresolved issue. Targeting nutritional support to the actual protein and energy needs improves the clinical outcome of critically ill patients, yet very few data are currently available on this topic in acute kidney injury. In this specific clinical condition the risk for underfeeding and overfeeding may be increased by factors interfering on nutrient need estimation, such as rapidly changing body weight due to fluid balance variations, nutrient losses and hidden calorie sources from renal replacement therapy. Moreover, as acute kidney injury is now considered a kidney-centered inflammatory syndrome, the renoprotective role of specific pharmaconutrients with anti-inflammatory properties remains to be fully defined. This review is aimed at discussing recently published results concerning quantitative and qualitative aspects of the nutritional approach to acute kidney injury in critically ill patients.

RECENT FINDINGS

Nutrient needs in patients with acute kidney injury can be difficult to estimate, and should be directly measured, especially in the ICU setting. In fact, recent findings suggest that hidden calorie sources not routinely taken into account - for example, calories from anticoagulants and replacement solutions for renal replacement therapy - could be quantitatively relevant in these patients. Moreover, recent experimental data indicate a possible role for some pharmaconutrients with anti-inflammatory effects (glutamine, and omega-3 fatty acids), in both the prevention of renal function worsening, and in the fostering of renal function recovery after an episode of acute kidney injury.

SUMMARY

Acute kidney injury includes a highly heterogeneous group of patients with widely varying nutrient needs and intakes. Nutritional requirements, in their quantitative and qualitative aspects, should be frequently assessed, individualized, and carefully integrated with renal replacement therapy, in order to avoid both underfeeding and overfeeding, as well as to exploit possible positive pharmacologic effects of specific nutrients.

Biochemical effects of phosphate-containing replacement fluid for continuous venovenous hemofiltration

AIMS

To examine biochemical effects of phosphate-containing replacement fluid (Phoxilium(®)) for continuous venovenous hemofiltration (CVVH).

METHODS

Retrospective comparison of respective serum biochemistry with sequential use of Accusol™ and Phoxilium, each over 48 h of CVVH.

RESULTS

We studied 15 critically ill patients. Accusol was switched to Phoxilium after 5 (4-8) days of CVVH. Respective serum biochemistry after 36-42 h of Accusol versus Phoxilium were: phosphate 1.02 (0.82-1.15) versus 1.44 (1.23-1.78) mmol/l, ionized calcium 1.28 (1.22-1.32) versus 1.12 (1.06-1.21) mmol/l, bicarbonate 24 (23-25) versus 20 (19-22) mmol/l, base excess 0 (-2 to 1) versus -4 (-6 to -3) mmol/l (p < 0.001). Cumulative phosphate intakes during respective periods were 69.6 (56.6-76.6) versus 67.2 (46.6-79.0) mmol (p = 0.45). Plasma strong ion differences were narrower with Phoxilium (p < 0.05), with similar strong ion gaps. No additional intravenous phosphate was given during Phoxilium use. Seven patients had serum phosphate >1.44 mmol/l.

CONCLUSIONS

Phoxilium versus Accusol use during CVVH effectively prevented hypophosphatemia but contributed to mild hyperphosphatemia, and is associated with relative hypocalcemia and metabolic acidosis.