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Local experience with the use of sustained low efficiency dialysis for acute renal failure
Intensive and Critical Care Nursing (2009) 25, 45—49
available at www.sciencedirect.com
journal homepage: www.elsevier.com/iccn
SERVICE IMPROVEMENT ARTICLE
Local experience with the use of sustained low efficiency dialysis for acute renal failure Reena Patel a,b,∗, Alison M. Pirret a,c, S. Mann a, Claire L. Sherring a a
Department of Intensive Care Medicine, Middlemore Hospital, New Zealand School of Nursing, University of Auckland, New Zealand c Massey University, New Zealand b
Accepted 7 September 2008
KEYWORDS Intensive and critical care nursing; Sustained low efficiency dialyis; Renal replacement therapy; Acute renal failure
Summary Renal replacement therapy (RRT) is a common therapy used to treat critically ill patients in acute renal failure. Currently a number of dialysis modalities are used such as haemodialysis, continuous renal replacement therapy (CRRT), and sustained low efficiency dialysis (SLED). As SLED is a recently implemented RRT, very little literature is available on the nursing aspects of SLED. This paper shares the local nursing experience of using SLED, thus providing a nursing perspective. Between 2002 and 2006, 103 patients were treated with SLED resulting in 307 SLED treatments. Early problems encountered involved patient hypotension, dialysis catheter patency and water quality; all of which were overcome by initially commencing dialysis at a lower prescribed blood pump rate, using larger catheters and improving water quality. Nursing advantages of SLED over CRRT included being able to release the patient for nursing activities and patient transfer out of the ICU for investigations and procedures; reduced nursing workload related to less machine and patient monitoring during the dialysis procedure; and cost reduction. Disadvantages of SLED are related to poor water quality, accessibility of water supply and limited space to house the two machines required. SLED has proven to be a nurse friendly dialysis modality for critically ill patients with acute renal failure. © 2008 Elsevier Ltd. All rights reserved.
Introduction Renal replacement therapy (RRT) is commonly used in the treatment of critically ill patients with acute renal failure in
∗ Corresponding author at: School of Nursing, Faculty of Medical & Health Science, University of Auckland, Private Bag 92019, Auckland, New Zealand. Tel.: +64 21 1026743. E-mail address: [email protected] (R. Patel).
intensive care. Currently a number of renal dialysis modalities are used, including intermittent haemodialysis (IHD), continuous renal replacement therapy (CRRT), and more recently sustained low efficiency dialysis (SLED). Although SLED (also known as extended daily diafiltration [EDD-f]) has been identified as the least utilised therapy (Ricci et al., 2006), recent literature demonstrating its effectiveness in the management of acute renal failure (ARF), is making this therapy increasingly popular. As the use of SLED is a recently implemented RRT (Davies and Leslie, 2008), very little
0964-3397/$ — see front matter © 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.iccn.2008.09.001
46
R. Patel et al.
literature is available on the nursing aspects of SLED. The aim of this paper is to share local nursing experience of using SLED as a renal dialysis modality in a tertiary seven-bed intensive care unit (ICU), thus providing a nursing perspective of SLED.
and/or ultrafiltration time, and can contribute to progression of ventilator weaning (Davies and Leslie, 2008; Dirkes and Hodge, 2007; Marshall et al., 2001).
Principles of dialysis
As already outlined, a number of renal dialysis modalities are used to treat ARF in the critically ill patient, including IHD, CRRT and SLED. There are numerous studies comparing IHD with CRRT; however there is limited literature surrounding SLED. Controversy remains over which modality is best suited to supporting the ICU patient (Davies and Leslie, 2008; Kellum et al., 2002; Ricci et al., 2006; Ricci and Ronco, 2008; Vanholder et al., 2001). In a survey conducted by Ricci et al. (2006), the dialysis modality most frequently used among specialists was CRRT (91%), followed by IHD (69%) and then SLED (24%), hence indicating preferences for use of more than one method of RRT. Factors that have been identified in determining which dialysis modalities are chosen by the specialists include: effectiveness of ultrafiltration and solute clearance, patient haemodynamic stability, time span of treatment, anticoagulation requirements, cost, and physician or unit familiarity of the equipment (Kellum et al., 2002; Ricci et al., 2006; Van Biesen et al., 2008; Vanholder et al., 2001). IHD is associated with hypotension and inadequate fluid removal, whereas CRRT is faced with problems of being labour intensive, with high costs of solutions, anti-coagulant medications, and reduced patient mobility due to the need for continuous therapy over a 24 h period (Davies and Leslie, 2008; Fliser and Kielstein, 2004). When reviewing effectiveness of dialysis systems, systematic reviews and meta-analysis have found no difference in mortality of critically ill patients when treated with IHD or CRRT (Bagshaw et al., 2008; Kellum et al., 2002; Tonelli et al., 2002; Van Biesen et al., 2008). Studies comparing SLED to CRRT have identified SLED as being able to provide effective daily treatment for patients with haemodynamic instability (Davies and Leslie, 2008; Marshall et al., 2001; Ponikvar, 2003). Several evaluative studies have also shown SLED to be less expensive than CRRT (Manns et al., 2003; Marshall et al., 2004). Although SLED requires the on-line quality control in the production of dialysate, SLED does not require the purchase of sterile dialysate/replacement fluid; hence cost savings can be made (Davies and Leslie, 2008). Unforeseen costs may occur when using CRRT if the circuit and replacement fluid are disposed of during interruption of treatment for surgical procedures, external diagnostic tests, and circuit downtime due to filter clotting (Ronco et al., 2006). During SLED treatments these costs can be avoided as sterile dialysate is delivered on-line, thus reducing the cost of wasting expensive CRRT fluid (Van Biesen et al., 2008). Research has demonstrated that the use of anticoagulants traditionally used in CRRT to prevent filter clotting, is reduced in SLED treatments, thus further reducing costs (Dirkes and Hodge, 2007; Fliser and Kielstein, 2004). Berbece and Richardson (2006) showed heparin could be avoided in 65% of SLED treatments with no significant adverse events. In summary, literature suggests CRRT is able to provide haemodynamic stability, solute removal, easy correction
All dialysis modalities use an extracorporeal circuit in which the blood travels from the patient, through a filter where dialysis occurs, and then returns to the patient. Dialysis is a process where the molecules in the blood diffuse across a semi-permeable membrane into a solution known as the dialysate using the principles of diffusion and convection (Pirret, 2005). Diffusion is a naturally occurring movement where solute moves across a semi-permeable membrane from a compartment of high concentration to a compartment of low concentration. Fluid in the dialysis compartment moves in a counter-current direction to blood flow to maintain a concentration gradient for diffusion to occur (Pirret, 2005). Convection (often referred to as ultrafiltration) is the movement of solute across a semi-permeable membrane in conjunction with a significant amount of water (Pirret, 2005). This movement occurs due to the hydrostatic pressure and the osmotic difference between the patient’s blood and the dialysate solution on the opposite side of the membrane. IHD relies on diffusion and requires moderate blood flow rates (200—300 ml/min) and high dialysate flow rates (500 ml/min) to maintain high concentration gradients. IHD provides rapid correction of electrolyte and acid base disturbances over a 3—4 h time period, allowing the patient to remain without dialysis for most of the day. However, the rapid fluid shifts can result in haemodynamic instability causing disequilibrium, thus risking cerebral oedema and increased intracranial pressure (Davies and Leslie, 2008; Pirret, 2005). CRRT relies on convection and has slower blood flow rates (100—200 ml/min) and slower dialysate flow rates (17—34 ml/min). Because of these lower blood and dialysate flow rates, CRRT can achieve blood purification without haemodynamic compromise and also prevent rapid alterations in fluid and electrolytes; therefore reducing the risk of disequilibrium. However, due to CRRT’s continuous nature, access to the patient and patient mobility is limited (Fliser and Kielstein, 2004; Pirret, 2005). SLED has evolved as a technical hybrid of CRRT and IHD (Bellomo and Ronco, 2000; Davies and Leslie, 2008), commonly using blood flow rates of 300 ml/min, counter-current dialysate rates of 200 ml/min and ultrafiltration rates of 100 ml/min. SLED combines the desirable components of both CRRT and IHD providing extended dialysis from 6 to 12 h (Bellomo and Ronco, 2000; Davies and Leslie, 2008). SLED has been purported not only to achieve ultrafiltration goals in patients with haemodynamic instability, but also to ensure low rates of solute clearance, thus minimising solute disequilibrium (Davies and Leslie, 2008; Marshall et al., 2004; Vanholder et al., 2001). The intermittent treatment can occur overnight, allowing patient freedom for transportation out of the unit for radiographic scanning, surgery or other procedures as required without compromising dialysis
Literature review
Local experience with the use of sustained low efficiency dialysis for acute renal failure of hypervolemia and SLED is able to provide all of these plus is less expensive and enables patient mobilisation (Fliser and Kielstein, 2004; Vanholder et al., 2001). However, although there is an increasing amount of literature on the benefits of SLED, there is minimal literature on the nursing perspective of using SLED as a RRT.
Local nursing experience of sustained low efficiency dialysis This paper describes the local experience of SLED in a sevenbed ICU of a 750 bed tertiary hospital, serving a population of 450,000. The ICU is a general ICU that also provides a tertiary ICU service for the national burns unit and the onsite paediatric facility. Prior to the introduction of SLED, most patients with ARF were being treated with CRRT over 3—5 days. The use of SLED began as an alternative dialysis option in 2002. Between May 2002 and December 2006 (inclusive), 103 patients were treated using SLED. Of these patients several had multiple treatments with the majority of patients requiring no more than one treatment in a 24-h period. During this time the total number of SLED treatments performed in the ICU was 307, with each patient receiving an average of 3.01 treatments (median 2, range 1—20). As the early literature on the suitability of SLED in the haemodynamically unstable ICU patient was controversial (Bellomo and Baldwin, 2002; Marshall et al., 2001), this ICU initially used SLED on the haemodynamically stable patient, while CRRT was used predominantly on the haemodynamically unstable patient. As literature began to emerge on the suitability of SLED in the haemodynamically unstable patient population (Marshall et al., 2001, 2004; Ponikvar, 2003), and medical and nursing experience and confidence with SLED increased, SLED began to be used as the first choice of RRT in patients with ARF, irrespective of haemodynamic stability and APACHE II scores. Early problems associated with hypotension during initial commencement of SLED in the ICU was resolved by starting at a lower than prescribed blood pump rate of 100 ml/min; then, depending on patient haemodynamic stability, the blood pump rate was increased to the prescribed 250—300 ml/min over a 5—60 min period. Of the SLED treatments prescribed (n = 307), 219 treatments were completed and 88 not completed. The majority of incomplete treatments were due to: filter clotting, patient venous catheter difficulties, premature discontinuation of patient treatment due to the need to transfer patients out of the unit for investigations and procedures, and water quality clogging the machine filter, thus affecting machine operation. Of these, filter clotting, patient venous catheter difficulties and premature discontinuation of patient treatment are also common to CRRT (Davies and Leslie, 2008; Dirkes and Hodge, 2007). However, the ICU’s early problems with venous catheter patency were encountered when smaller dialysis catheters (12 Fr: 16 cm) were used. As catheter size and diameter can limit flow rates (Pirret, 2005), and SLED required higher blood flow rates than CRRT, this problem was significantly reduced following the introduction of larger catheters (13.5 Fr: 15 cm for subclavian access and 24 cm for femoral access).
47
As SLED uses tap water and a reverse osmosis (RO) unit to produce sterile dialysate, poor tap water quality into the RO machine can block filters and result in machine failure. The ICU’s early problems related to premature discontinuation of patient treatments due to poor water quality clogging the machine has been partially averted with provision of a more efficient pump to deliver higher quality water. However, as water quality influences the functioning of the RO unit and therefore treatment processes (Davies and Leslie, 2008), ICU’s that have poor tap water quality may have limited success in using SLED as an RRT. The average length of each SLED treatment was 7 h (median 8, range 2—13). When compared to CRRT, SLED allowed the patient to be dialysis-free for an average of 17 h per day, enabling patient freedom for transportation out of the unit for radiographic scanning, surgery or other procedures as required, mobilisation and progression of ventilator weaning (Davies and Leslie, 2008; Dirkes and Hodge, 2007; Marshall et al., 2001). Since introducing the SLED as a RRT, the ICU has identified cost savings similar to those reported in other literature (Manns et al., 2003; Marshall et al., 2004). As the SLED produces it own dialysate from tap water and the RO unit, it does not require the purchase of dialysate/replacement fluid. Because of this, at July 2007 the cost of SLED treatment over a 24 h period was $224.70 compared to $499.70 for the CRRT treatment, thus supporting the findings of both Manns et al. (2003) and Marshall et al. (2004), who found SLED treatment cheaper than that of CRRT. As the SLED machine was only used for an average of 7 h per treatment and has a hot disinfectant cycle taking approximately 30 min that sterilises the machine, it can be used on more than one patient within a 24-h period. Thus using SLED rather than CRRT reduces the number of RRT machines required to dialyse the critically ill patient; with the potential to reduce capital expenditure and ongoing machine maintenance costs. Prior to the introduction of SLED, stable patients with ARF were dialysed using CRRT or IHD. Although CRRT was set up and managed by ICU nursing staff, IHD was set up and managed by dialysis unit nurses or technicians. Since using the SLED in the ICU, requests of the dialysis service for IHD has significantly reduced placing less demands on both haemodialysis machines and staff. This is an important consideration, as it not only frees up valuable haemodialysis resources but as SLED is set up and managed by ICU staff, it enables more timely and convenient ICU dialysis regimes.
Nursing responsibilities associated with SLED Like CRRT, SLED is able to be set up by the nursing staff at the bedside. The assembly of SLED treatment requires the SLED machine and a reverse osmosis unit that can be attached to hospital plumbing that enables access to tap water (Fig. 1). As SLED requires both a SLED and RO machine, the need to accommodate two pieces of equipment within a bed space may be problematic in ICU’s where space is limited. Currently our ICU only has three areas in the unit that have the required plumbing that enables connection of the RO unit to tap water. This has the disadvantage of having to relocate unstable critically ill patients to a bed space that has
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R. Patel et al.
Figure 1
Reverse osmosis unit and SLED dialysis procedure.
access to the required plumbing facilities. However, the ICU is shortly moving to a new purpose built facility, in which the RO unit is centrally located with internal plumbing enabling connection access between every second bed space. Hence, patients will no longer have to be relocated to enable SLED to be implemented. The RO unit provides a constant source of purified water (Tolwani et al., 2007) and enters the SLED producing its own dialysate via an on-line bicarbonate proportioning system (Davies and Leslie, 2008; Tolwani et al., 2007). It delivers the prescribed solution into the circuit and removes wastewater as effluent via a pipe directly into the hospital drainage system. The nurse is not required to change effluent drainage bags or dialysate/replacement fluid bags, thus freeing up nursing time for other patient care activities. As SLED, when compared to CRRT, does not require the replacement of 5 l dialysate/replacement solu-
tion bags and emptying of 5 l effluent bags; it provides the advantage of reducing the potential for strain and splash injuries. For all RRT in our unit, the dialysis prescription is determined by the intensivist, and includes filtration rate, blood pump rate, fluid removal goal as required, and the duration of dialysis treatment, which is usually prescribed for 8 h. Nursing care responsibilities during SLED treatment are similar to those required during CRRT of which have been previously outlined in the literature (Dirkes and Hodge, 2007). Like many CRRT machines, the SLED machine has an internal set up, monitoring and disconnection screens to assist the nurse with these processes. However, as the SLED regime is prescribed at 8 h, when compared to CRRT the nursing workload related to patient and machine monitoring during the dialysis process is reduced.
Local experience with the use of sustained low efficiency dialysis for acute renal failure
Conclusion SLED is becoming an increasingly popular RRT and although literature is emerging on the use of SLED, there is little literature from a nursing perspective. The aim of this paper is to share local nursing experience of using SLED as a RRT, thus contributing to nursing knowledge on a new dialysis modality. Since the introduction of SLED in 2002 nursing staff have become increasingly familiar with SLED, and it is now viewed by nursing staff as the preferred dialysis modality for patients requiring renal support. This is firstly due to being able to release the patient for nursing activities and patient transfer out of the ICU for investigations and procedures and secondly, the reduced nursing workload related to decreased machine and patient monitoring during the dialysis procedure. As the nursing literature on SLED is scant much of the local nursing experience shared in this paper is anecdotal. However, it is only by sharing these experiences can nursing knowledge be expanded and patient outcomes improved.
Conflict of interest None.
Acknowledgements The authors would like to acknowledge Dr. Mark Marshall and Maggie Ma for providing the statistical data used in this paper and Anthony Cribb for the graphic illustration.
References Bagshaw SM, Berthiaume LR, Delaney A, Bellomo R. Continuous versus intermittent renal replacement therapy for critically ill patients with acute kidney injury: a meta-analysis. Critical Care Medicine 2008;36(2):610—7. Bellomo R, Baldwin I. Sustained low efficiency dialysis in the ICU. International Journal of Intensive Care 2002(Winter):181—7. Bellomo R, Ronco C. Continuous haemofiltration in the intensive care unit. Critical Care 2000;4:339—45. Berbece AN, Richardson RMA. Sustained low-efficiency dialysis in the ICU: cost, anticoagulation, and solute removal. Kidney International 2006;70:963—8. Davies HT, Leslie GD. Intermittent versus continuous renal replacement therapy: a matter of controversy. Intensive and Critical Care Nursing 2008;24(5):269—85.
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Dirkes SM, Hodge K. Continuous renal replacement therapy in the adult intensive care unit-history and current trends. Critical Care Nurse 2007;27(2):61—80. Fliser D, Kielstein JT. A single-pass batch dialysis system: an ideal dialysis method for the patient in intensive care with acute renal failure. Current Opinion Critical Care 2004;10:483—8. Kellum JA, Angus DC, Johnson JP, Leblanc M, Griffin M, Ramakrishnan N, et al. Continuous versus intermittent renal replacement therapy: a meta-analysis. Intensive Care Medicine 2002;28:29—37. Manns B, Doig C, Lee H, Dean S, Tonelli M, Johnson D, et al. Cost of acute renal failure requiring dialysis in the intensive care unit: clinical and resource implications of renal recovery. Critical Care Medicine 2003;31(2):449—55. Marshall MR, Golper TA, Shaver MJ, Alam MG, Chatoth DK. Sustained low-efficiency dialysis for critically ill patients requiring renal replacement therapy. Kidney International 2001;60: 777—85. Marshall MR, Ma T, Galler D, Rankin APN, Williams AB. Sustained lowefficiency daily diafiltration (SLEDD-f) for critically ill patients requiring renal replacement therapy: towards an adequate therapy. Nephrology Dialysis Transplant 2004;19:877—84. Pirret AM. Acute care nursing: a physiological approach to clinical assessment and patient care. Auckland, New Zealand: Author, 2005. Ponikvar R. Blood purification in the intensive care unit. Nephrology Dialysis Transplant 2003;18(Suppl. 5):v63—7. Ricci Z, Ronco C, D’Amico G, De Felice R, Rossi S, Bolgan I, et al. Practice patterns in the management of acute renal failure in the critically ill patient: an international survey. Nephrology Dialysis Transplant 2006;21:690—6. Ricci Z, Ronco C. Dose and efficiency of renal replacement therapy: continuous renal replacement therapy versus intermittent hemodialysis versus slow extended dialysis. Critical Care Medicine 2008;36(4):S229—37. Ronco C, Ricci Z, Bellomo R. Current worldwide practice of dialysis dose prescription in acute renal failure. Current Opinion Critical Care 2006;12:551—6. Tolwani AJ, Wheeler TS, Wille KM. Sustained low-efficiency dialysis. Acute Kidney Injury Contributions to Nephrology 2007;156:320—4. Tonelli M, Manns B, Feller-Kopman D. Acute renal failure in the intensive car unit: a systematic review of the impact of dialytic modality on morality and renal recovery. American Journal of Kidney Diseases 2002;40(5):875—85. Van Biesen WV, Lameire N, Vanholder R. A tantalizing question: Ferrari or Rolls Rocye? A meta-analysis on the ideal renal replacement modality for acute kidney injury at the intensive care unit. Critical Care Medicine 2008;36(2):649—50. Vanholder R, Van Biesen W, Lameire N. What is the renal replacement method of first choice for intensive care patients? Journal of the American Society of Nephrology 2001;12:S40—3.
available at www.sciencedirect.com
journal homepage: www.elsevier.com/iccn
SERVICE IMPROVEMENT ARTICLE
Local experience with the use of sustained low efficiency dialysis for acute renal failure Reena Patel a,b,∗, Alison M. Pirret a,c, S. Mann a, Claire L. Sherring a a
Department of Intensive Care Medicine, Middlemore Hospital, New Zealand School of Nursing, University of Auckland, New Zealand c Massey University, New Zealand b
Accepted 7 September 2008
KEYWORDS Intensive and critical care nursing; Sustained low efficiency dialyis; Renal replacement therapy; Acute renal failure
Summary Renal replacement therapy (RRT) is a common therapy used to treat critically ill patients in acute renal failure. Currently a number of dialysis modalities are used such as haemodialysis, continuous renal replacement therapy (CRRT), and sustained low efficiency dialysis (SLED). As SLED is a recently implemented RRT, very little literature is available on the nursing aspects of SLED. This paper shares the local nursing experience of using SLED, thus providing a nursing perspective. Between 2002 and 2006, 103 patients were treated with SLED resulting in 307 SLED treatments. Early problems encountered involved patient hypotension, dialysis catheter patency and water quality; all of which were overcome by initially commencing dialysis at a lower prescribed blood pump rate, using larger catheters and improving water quality. Nursing advantages of SLED over CRRT included being able to release the patient for nursing activities and patient transfer out of the ICU for investigations and procedures; reduced nursing workload related to less machine and patient monitoring during the dialysis procedure; and cost reduction. Disadvantages of SLED are related to poor water quality, accessibility of water supply and limited space to house the two machines required. SLED has proven to be a nurse friendly dialysis modality for critically ill patients with acute renal failure. © 2008 Elsevier Ltd. All rights reserved.
Introduction Renal replacement therapy (RRT) is commonly used in the treatment of critically ill patients with acute renal failure in
∗ Corresponding author at: School of Nursing, Faculty of Medical & Health Science, University of Auckland, Private Bag 92019, Auckland, New Zealand. Tel.: +64 21 1026743. E-mail address: [email protected] (R. Patel).
intensive care. Currently a number of renal dialysis modalities are used, including intermittent haemodialysis (IHD), continuous renal replacement therapy (CRRT), and more recently sustained low efficiency dialysis (SLED). Although SLED (also known as extended daily diafiltration [EDD-f]) has been identified as the least utilised therapy (Ricci et al., 2006), recent literature demonstrating its effectiveness in the management of acute renal failure (ARF), is making this therapy increasingly popular. As the use of SLED is a recently implemented RRT (Davies and Leslie, 2008), very little
0964-3397/$ — see front matter © 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.iccn.2008.09.001
46
R. Patel et al.
literature is available on the nursing aspects of SLED. The aim of this paper is to share local nursing experience of using SLED as a renal dialysis modality in a tertiary seven-bed intensive care unit (ICU), thus providing a nursing perspective of SLED.
and/or ultrafiltration time, and can contribute to progression of ventilator weaning (Davies and Leslie, 2008; Dirkes and Hodge, 2007; Marshall et al., 2001).
Principles of dialysis
As already outlined, a number of renal dialysis modalities are used to treat ARF in the critically ill patient, including IHD, CRRT and SLED. There are numerous studies comparing IHD with CRRT; however there is limited literature surrounding SLED. Controversy remains over which modality is best suited to supporting the ICU patient (Davies and Leslie, 2008; Kellum et al., 2002; Ricci et al., 2006; Ricci and Ronco, 2008; Vanholder et al., 2001). In a survey conducted by Ricci et al. (2006), the dialysis modality most frequently used among specialists was CRRT (91%), followed by IHD (69%) and then SLED (24%), hence indicating preferences for use of more than one method of RRT. Factors that have been identified in determining which dialysis modalities are chosen by the specialists include: effectiveness of ultrafiltration and solute clearance, patient haemodynamic stability, time span of treatment, anticoagulation requirements, cost, and physician or unit familiarity of the equipment (Kellum et al., 2002; Ricci et al., 2006; Van Biesen et al., 2008; Vanholder et al., 2001). IHD is associated with hypotension and inadequate fluid removal, whereas CRRT is faced with problems of being labour intensive, with high costs of solutions, anti-coagulant medications, and reduced patient mobility due to the need for continuous therapy over a 24 h period (Davies and Leslie, 2008; Fliser and Kielstein, 2004). When reviewing effectiveness of dialysis systems, systematic reviews and meta-analysis have found no difference in mortality of critically ill patients when treated with IHD or CRRT (Bagshaw et al., 2008; Kellum et al., 2002; Tonelli et al., 2002; Van Biesen et al., 2008). Studies comparing SLED to CRRT have identified SLED as being able to provide effective daily treatment for patients with haemodynamic instability (Davies and Leslie, 2008; Marshall et al., 2001; Ponikvar, 2003). Several evaluative studies have also shown SLED to be less expensive than CRRT (Manns et al., 2003; Marshall et al., 2004). Although SLED requires the on-line quality control in the production of dialysate, SLED does not require the purchase of sterile dialysate/replacement fluid; hence cost savings can be made (Davies and Leslie, 2008). Unforeseen costs may occur when using CRRT if the circuit and replacement fluid are disposed of during interruption of treatment for surgical procedures, external diagnostic tests, and circuit downtime due to filter clotting (Ronco et al., 2006). During SLED treatments these costs can be avoided as sterile dialysate is delivered on-line, thus reducing the cost of wasting expensive CRRT fluid (Van Biesen et al., 2008). Research has demonstrated that the use of anticoagulants traditionally used in CRRT to prevent filter clotting, is reduced in SLED treatments, thus further reducing costs (Dirkes and Hodge, 2007; Fliser and Kielstein, 2004). Berbece and Richardson (2006) showed heparin could be avoided in 65% of SLED treatments with no significant adverse events. In summary, literature suggests CRRT is able to provide haemodynamic stability, solute removal, easy correction
All dialysis modalities use an extracorporeal circuit in which the blood travels from the patient, through a filter where dialysis occurs, and then returns to the patient. Dialysis is a process where the molecules in the blood diffuse across a semi-permeable membrane into a solution known as the dialysate using the principles of diffusion and convection (Pirret, 2005). Diffusion is a naturally occurring movement where solute moves across a semi-permeable membrane from a compartment of high concentration to a compartment of low concentration. Fluid in the dialysis compartment moves in a counter-current direction to blood flow to maintain a concentration gradient for diffusion to occur (Pirret, 2005). Convection (often referred to as ultrafiltration) is the movement of solute across a semi-permeable membrane in conjunction with a significant amount of water (Pirret, 2005). This movement occurs due to the hydrostatic pressure and the osmotic difference between the patient’s blood and the dialysate solution on the opposite side of the membrane. IHD relies on diffusion and requires moderate blood flow rates (200—300 ml/min) and high dialysate flow rates (500 ml/min) to maintain high concentration gradients. IHD provides rapid correction of electrolyte and acid base disturbances over a 3—4 h time period, allowing the patient to remain without dialysis for most of the day. However, the rapid fluid shifts can result in haemodynamic instability causing disequilibrium, thus risking cerebral oedema and increased intracranial pressure (Davies and Leslie, 2008; Pirret, 2005). CRRT relies on convection and has slower blood flow rates (100—200 ml/min) and slower dialysate flow rates (17—34 ml/min). Because of these lower blood and dialysate flow rates, CRRT can achieve blood purification without haemodynamic compromise and also prevent rapid alterations in fluid and electrolytes; therefore reducing the risk of disequilibrium. However, due to CRRT’s continuous nature, access to the patient and patient mobility is limited (Fliser and Kielstein, 2004; Pirret, 2005). SLED has evolved as a technical hybrid of CRRT and IHD (Bellomo and Ronco, 2000; Davies and Leslie, 2008), commonly using blood flow rates of 300 ml/min, counter-current dialysate rates of 200 ml/min and ultrafiltration rates of 100 ml/min. SLED combines the desirable components of both CRRT and IHD providing extended dialysis from 6 to 12 h (Bellomo and Ronco, 2000; Davies and Leslie, 2008). SLED has been purported not only to achieve ultrafiltration goals in patients with haemodynamic instability, but also to ensure low rates of solute clearance, thus minimising solute disequilibrium (Davies and Leslie, 2008; Marshall et al., 2004; Vanholder et al., 2001). The intermittent treatment can occur overnight, allowing patient freedom for transportation out of the unit for radiographic scanning, surgery or other procedures as required without compromising dialysis
Literature review
Local experience with the use of sustained low efficiency dialysis for acute renal failure of hypervolemia and SLED is able to provide all of these plus is less expensive and enables patient mobilisation (Fliser and Kielstein, 2004; Vanholder et al., 2001). However, although there is an increasing amount of literature on the benefits of SLED, there is minimal literature on the nursing perspective of using SLED as a RRT.
Local nursing experience of sustained low efficiency dialysis This paper describes the local experience of SLED in a sevenbed ICU of a 750 bed tertiary hospital, serving a population of 450,000. The ICU is a general ICU that also provides a tertiary ICU service for the national burns unit and the onsite paediatric facility. Prior to the introduction of SLED, most patients with ARF were being treated with CRRT over 3—5 days. The use of SLED began as an alternative dialysis option in 2002. Between May 2002 and December 2006 (inclusive), 103 patients were treated using SLED. Of these patients several had multiple treatments with the majority of patients requiring no more than one treatment in a 24-h period. During this time the total number of SLED treatments performed in the ICU was 307, with each patient receiving an average of 3.01 treatments (median 2, range 1—20). As the early literature on the suitability of SLED in the haemodynamically unstable ICU patient was controversial (Bellomo and Baldwin, 2002; Marshall et al., 2001), this ICU initially used SLED on the haemodynamically stable patient, while CRRT was used predominantly on the haemodynamically unstable patient. As literature began to emerge on the suitability of SLED in the haemodynamically unstable patient population (Marshall et al., 2001, 2004; Ponikvar, 2003), and medical and nursing experience and confidence with SLED increased, SLED began to be used as the first choice of RRT in patients with ARF, irrespective of haemodynamic stability and APACHE II scores. Early problems associated with hypotension during initial commencement of SLED in the ICU was resolved by starting at a lower than prescribed blood pump rate of 100 ml/min; then, depending on patient haemodynamic stability, the blood pump rate was increased to the prescribed 250—300 ml/min over a 5—60 min period. Of the SLED treatments prescribed (n = 307), 219 treatments were completed and 88 not completed. The majority of incomplete treatments were due to: filter clotting, patient venous catheter difficulties, premature discontinuation of patient treatment due to the need to transfer patients out of the unit for investigations and procedures, and water quality clogging the machine filter, thus affecting machine operation. Of these, filter clotting, patient venous catheter difficulties and premature discontinuation of patient treatment are also common to CRRT (Davies and Leslie, 2008; Dirkes and Hodge, 2007). However, the ICU’s early problems with venous catheter patency were encountered when smaller dialysis catheters (12 Fr: 16 cm) were used. As catheter size and diameter can limit flow rates (Pirret, 2005), and SLED required higher blood flow rates than CRRT, this problem was significantly reduced following the introduction of larger catheters (13.5 Fr: 15 cm for subclavian access and 24 cm for femoral access).
47
As SLED uses tap water and a reverse osmosis (RO) unit to produce sterile dialysate, poor tap water quality into the RO machine can block filters and result in machine failure. The ICU’s early problems related to premature discontinuation of patient treatments due to poor water quality clogging the machine has been partially averted with provision of a more efficient pump to deliver higher quality water. However, as water quality influences the functioning of the RO unit and therefore treatment processes (Davies and Leslie, 2008), ICU’s that have poor tap water quality may have limited success in using SLED as an RRT. The average length of each SLED treatment was 7 h (median 8, range 2—13). When compared to CRRT, SLED allowed the patient to be dialysis-free for an average of 17 h per day, enabling patient freedom for transportation out of the unit for radiographic scanning, surgery or other procedures as required, mobilisation and progression of ventilator weaning (Davies and Leslie, 2008; Dirkes and Hodge, 2007; Marshall et al., 2001). Since introducing the SLED as a RRT, the ICU has identified cost savings similar to those reported in other literature (Manns et al., 2003; Marshall et al., 2004). As the SLED produces it own dialysate from tap water and the RO unit, it does not require the purchase of dialysate/replacement fluid. Because of this, at July 2007 the cost of SLED treatment over a 24 h period was $224.70 compared to $499.70 for the CRRT treatment, thus supporting the findings of both Manns et al. (2003) and Marshall et al. (2004), who found SLED treatment cheaper than that of CRRT. As the SLED machine was only used for an average of 7 h per treatment and has a hot disinfectant cycle taking approximately 30 min that sterilises the machine, it can be used on more than one patient within a 24-h period. Thus using SLED rather than CRRT reduces the number of RRT machines required to dialyse the critically ill patient; with the potential to reduce capital expenditure and ongoing machine maintenance costs. Prior to the introduction of SLED, stable patients with ARF were dialysed using CRRT or IHD. Although CRRT was set up and managed by ICU nursing staff, IHD was set up and managed by dialysis unit nurses or technicians. Since using the SLED in the ICU, requests of the dialysis service for IHD has significantly reduced placing less demands on both haemodialysis machines and staff. This is an important consideration, as it not only frees up valuable haemodialysis resources but as SLED is set up and managed by ICU staff, it enables more timely and convenient ICU dialysis regimes.
Nursing responsibilities associated with SLED Like CRRT, SLED is able to be set up by the nursing staff at the bedside. The assembly of SLED treatment requires the SLED machine and a reverse osmosis unit that can be attached to hospital plumbing that enables access to tap water (Fig. 1). As SLED requires both a SLED and RO machine, the need to accommodate two pieces of equipment within a bed space may be problematic in ICU’s where space is limited. Currently our ICU only has three areas in the unit that have the required plumbing that enables connection of the RO unit to tap water. This has the disadvantage of having to relocate unstable critically ill patients to a bed space that has
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R. Patel et al.
Figure 1
Reverse osmosis unit and SLED dialysis procedure.
access to the required plumbing facilities. However, the ICU is shortly moving to a new purpose built facility, in which the RO unit is centrally located with internal plumbing enabling connection access between every second bed space. Hence, patients will no longer have to be relocated to enable SLED to be implemented. The RO unit provides a constant source of purified water (Tolwani et al., 2007) and enters the SLED producing its own dialysate via an on-line bicarbonate proportioning system (Davies and Leslie, 2008; Tolwani et al., 2007). It delivers the prescribed solution into the circuit and removes wastewater as effluent via a pipe directly into the hospital drainage system. The nurse is not required to change effluent drainage bags or dialysate/replacement fluid bags, thus freeing up nursing time for other patient care activities. As SLED, when compared to CRRT, does not require the replacement of 5 l dialysate/replacement solu-
tion bags and emptying of 5 l effluent bags; it provides the advantage of reducing the potential for strain and splash injuries. For all RRT in our unit, the dialysis prescription is determined by the intensivist, and includes filtration rate, blood pump rate, fluid removal goal as required, and the duration of dialysis treatment, which is usually prescribed for 8 h. Nursing care responsibilities during SLED treatment are similar to those required during CRRT of which have been previously outlined in the literature (Dirkes and Hodge, 2007). Like many CRRT machines, the SLED machine has an internal set up, monitoring and disconnection screens to assist the nurse with these processes. However, as the SLED regime is prescribed at 8 h, when compared to CRRT the nursing workload related to patient and machine monitoring during the dialysis process is reduced.
Local experience with the use of sustained low efficiency dialysis for acute renal failure
Conclusion SLED is becoming an increasingly popular RRT and although literature is emerging on the use of SLED, there is little literature from a nursing perspective. The aim of this paper is to share local nursing experience of using SLED as a RRT, thus contributing to nursing knowledge on a new dialysis modality. Since the introduction of SLED in 2002 nursing staff have become increasingly familiar with SLED, and it is now viewed by nursing staff as the preferred dialysis modality for patients requiring renal support. This is firstly due to being able to release the patient for nursing activities and patient transfer out of the ICU for investigations and procedures and secondly, the reduced nursing workload related to decreased machine and patient monitoring during the dialysis procedure. As the nursing literature on SLED is scant much of the local nursing experience shared in this paper is anecdotal. However, it is only by sharing these experiences can nursing knowledge be expanded and patient outcomes improved.
Conflict of interest None.
Acknowledgements The authors would like to acknowledge Dr. Mark Marshall and Maggie Ma for providing the statistical data used in this paper and Anthony Cribb for the graphic illustration.
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