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ACUTE RENAL FAILURE: METHODS OF TREATMENT IN THE INTENSIVE CARE UNIT Sofia Zyga1, Paul Sarafis1, John Stathoulis2, Peter Kolovos1, Dimitris Theophilopoulos3 Nursing School, University of Peloponnese, Sparta, Greece 2 Biomedical Engineering Department, Sparta General Hospital, Sparta, Greece 3 Haemodialysis Unit, Sparta General Hospital, Sparta, Greece
1
Zyga S., Sarafis P., Stathoulis J., Kolovos P., Theophilopoulos D. (2009). Acute renal failure: methods of treatment in the intensive care unit. Journal of Renal Care 35(2), 60–66.
SUMMARY Patients who are treated in an intensive care unit (ICU) show the need of recovery of their renal function. The reason is that, in this particular cohort of patients, we have to maintain the necessary balance between body fluids, electrolytes, and acidbase, try to suspend further renal damage and purify the patient’s blood to better accept the given therapy. In this paper, we try to demonstrate all the methods that can be used depending on the patient’s condition, the therapist’s preferences and the hospital’s capabilities.
K E Y W O R D S Acute renal failure • Haemodialysis • Nursing
INTRODUCTION Acute renal failure (ARF) remains one of the major challenges of modern medicine (Ronco 2007). In the intensive care unit (ICU), the uraemic complications of ARF aggravate the clinical and haemodynamic status of critically ill patients and impede their clinical recovery (Stefan & Eckardt 2007). It is estimated that 10–30% of patients with ARF in the ICU of a general hospital will need a renal replacement therapy (RRT). The objectives of renal function substitution are:
B I O D ATA Sofia Zyga has worked as a renal nurse since 1998. She has a Postgraduate Degree in Organization and of Health Services Administration and also a Ph.D. in clinical nephrology. She has presented a number of papers at a national and international level and has also published many papers in Greek journals. She is an Assistant Professor in Fundamentals of Nursing at the University of Peloponnese. CORRESPONDENCE
Sofia Zyga Nursing School, University of Peloponnese, Sparta, Laconia 23100, Greece Tel.: 00302731021208 Fax: 00302731089719
[email protected] /
[email protected]
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• To maintain a balance for fluids, electrolytes and acid-base • To suspend further progression of renal damage • To re-establish normal renal functions (Clermont et al. 2002; Metcalfe et al. 2002; Pruchnicki & Dasta 2002) The indications to use the most recent methods used to treat ARF patients are the following: • • • • •
Anuria or nondecongestant oliguria Severe metabolic acidosis (pH >7.1) Uraemia (blood urea nitrogen >30 mmol/l) Potassaemia (K+ serum >6.5 mmol/l or rapid increase of K+) Hypernatraemia (Na+ serum >160 mmol/l) or hyponatraemia (Na+ serum >115 mmol/l), parenteral intake of food and transfusion of large volumes of blood
The above indications are strictly predefined and demand immediate and aggressive renal intervention (Hou et al. 1983; Shusterman et al. 1987; Brivet et al. 1996; Burchardi 2001; Vincent 2001). Discounting the cause of the primary illness, ARF constitutes an additional aggravating factor that increases hospital mortality (Metnitz et al. 2002). The imbalance of the water and electrolytes homeostasis constitutes the main expression of ARF and is accountable for its high mortality (30–90%) (Anderson & Schrier 1997).
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An observational study was conducted with ICU patients who were either treated with RRT or fulfilled at least one of the defined criteria for ARF. This took place from September 2000 to December 2001 at 54 hospitals in 23 countries. In this multinational study, the period of ARF prevalence that required RRT in the ICU was between 5% and 6% and was associated with a high hospital mortality rate (Shigehiko et al. 2005). The value of each method of RRT depends on the patients’ general situation and their individual problems. However, it should be emphasised that in most cases the differences between the various methods of RRT are insignificant, and the method of treatment applied depends on the experience of each centre. Because greater cardiovascular instability is presented at the beginning of haemodialysis (HD) treatment, the most suitable methods of RRT are peritoneal clearance and continuous venovenous haemofiltration (CVVH). However, after the patient is stabilised, then HD can also be used.
METHODS OF RENAL FUNCTION SUBSTITUTION After reviewing the recent literature, it is possible to claim that less attention has been given to ARF of ICU patients (Bellomo & Ronco 1996). Today, the limited reports concerning ARF in the ICU are due to the following reasons: • Epidemiological (late HD initiation, insufficient substitution of renal function and delayed re-establishment of renal function) • Technical (application of conventional HD, insufficiency of continuous methods, membrane bioincompatibility, the use of nonadsorptive membranes and the need for the use of continuous heparin) • Therapeutic (small populations and the diverse variation of patients) (Bellomo & Ronco 1996) The methods of renal function substitution used today are the following: • Continuous renal replacement therapies (continuous arteriovenous blood filtration and continuous arteriovenous HD) • Intermitted HD • Haemofiltration of large volumes and peritoneal dialysis (PD)
All methods have their advantages and disadvantages. The selection of the method depends on the clinical condition of the patient, the nephrologists’ therapy preferences and the capabilities of each hospital (Clark et al. 1998; Liaño & Pascual 1998; Albright 2001; Tonelli et al. 2001). CONTINUOUS ARTERIOVENOUS HAEMOFILTRATION (CAVH) It is a simple, secure, manageable method and can also be used in small and isolated hospitals without particularly specialised personnel. It may be used on critically ill patients who are haemodynamically unstable (arterial pressure and heart rate fluctuations), such as those with acute pulmonary oedema, congestive heart failure, septic shock, and oliguric states. CAVH, in contrast to HD, does not involve the use of blood pumps but uses the patient’s own mean arterial pressure to generate a driving force across the haemofilter membrane. CAVH can remove excess fluid and uraemic toxins. Fluid removal by CAVH is characterised by the slow, continuous process of ultrafiltration, thus it avoids the risk of hypotension, muscle cramps, or disequilibrium syndrome. Furthermore, CAVH does not require fluid restriction, allowing for increased administration of parenteral nutrition and intravenous medications; nor does it require expensive equipment or highly trained personnel. Although CAVH membrane materials may differ, they all permit the removal of plasma and nonproteinbound solutes with molecular weight less than 10,000 Da. CAVH can be applied for 24 hours per day for several days. In addition, small-size haemofilters are used (hollow fibre membranes with a surface area of 0.2–0.5 m2). These have a high hydraulic permeability coefficient and give a convective clearance of the extracorporeal blood circuit without a blood pump. However, fluid substitution and the continuous infusion of heparin at a rate of 10 IU/kg/h are required. The blood flows through the extracorporeal circuit due to the patient’s systemic blood pressure. A blood flow of 20–90 ml/min is sufficient to produce ultrafiltration. CAVH is considered the most appropriate method for the patient when the desired quantity of ultrafiltrate is greater than 500 ml/h. Advantages The valuation of CAVH depends on its ability to maintain concentrations of uraemic toxins in the blood at acceptable low levels and simultaneously achieve a normal balance between fluids and electrolytes. It rapidly corrects metabolic acidosis without the need to remove large volumes of plasma and
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provides cardiovascular stability by increasing the cardiac output and by minimising peripheral resistance. Disadvantages In cases of parenteral nutrition, 2–10% of amino acids are lost by ultrafiltration. CAVH also can remove pharmacological agents from the blood; however, only the nonprotein-bound fraction of the drug has the potential to be cleared from the blood stream by CAVH. To prevent blood from clotting in the haemofilter, most patients will require administration of heparin, which in some patients may increase the possibility of haemorrhage. Important clinical problems are: blood clotting of the small-size haemofilters with their large number of hollow fibre membranes and low clearances of small molecular substances (Bellomo & Ronco 2000). CONTINUOUS ARTERIOVENOUS HAEMODIALYSIS (CAVHD) The removal of soluble substances from the plasma is mainly accomplished with continuous diffusion. It requires the use of a haemofilter with a high hydraulic permeability coefficient. Advantages High clearance of uraemic toxins and removal of small volumes of ultrafiltrate (90 mmHg to perfuse circuit, and heparin infusion and greatly increases work for an ICU nurse. The arterial access presents complications such as infections, thrombosis, laceration and distal ischaemia. INTERMITTENT HAEMODIALYSIS (IHD) This therapy is preferred by most nephrologists. The most common clinical practice consists of daily long and specially designed sessions that ensure haemodynamic stability.
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The technique of this method involves an HD machine with all the latest technology to ensure the vascular stability of the critical ill patient—high-flux haemofilters and vascular access (percutaneous cannulation of the inner jugular, subclavian or femoral vein) (Schortgen et al. 2000). Advantages During IHD, blood flows rapidly round the machine, where waste products and excess fluids are removed, thus restoring the electrolyte and pH balance. The work ordinarily done by the kidneys during 48 hours is compressed into 3– 4 hours. Disadvantages The IHD method may lead to haemodynamic instability because of the removal of 3–6 litres of fluid per session. This rapid removal of fluids may lead to hypotension, and this is the primary reason that IHD should not be used in patients with a mean arterial pressure below 90–95 mmHg. IHD may not remove enough fluid to relieve the fluid overload caused by kidney failure. Therefore, the delivery of parenteral nutrition may be restricted, which may contribute to malnutrition in acutely ill patients. The rapid removal of solutes and fluids can result in dialysis disequilibrium syndrome, a disorder affecting the central nervous system. Electrolyte imbalance may also induce cardiac arrhythmias. CONTINUOUS VENOVENOUS HAEMODIAFILTRATION (CVVHD) This is similar to CVVH but combines diffusion and convection. Blood and dialysate fluid are circulated in a countercurrent fashion. As with CVVH, a transmembrane pressure is applied that permits large volumes of fluid to be ultrafiltrated. Replacement fluid is reinfused at a rate dependent on the volume of fluid to be removed. Advantages The membranes of these filters have excellent compatibility (polysulphone and polyacrylonitrile); therefore, leucopoenia and hypoxaemia, which may occur in HD, are unlikely to occur. During the initial phase of treatment, there is little cardiovascular instability. Finally, this method permits the patients with ARF to partake of free fluids.
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Disadvantages CVVHD requires continuous heparin infusion. The fast removal of fluid will result in changes in arterial pressure and heart rate. All these factors emphasise the need of a specialised personnel who should deal exclusively with the patient during treatment. Another disadvantage is the relatively low clearance that can be achieved with CVVHD (10–15 ml/min), except when this method is modified with continuous HD (CVVH), where the cleansing of blood is increased (25–30 ml/min). Finally, if this treatment is prolonged, despite preliminary cardiovascular stability, hypotension can manifest itself. Therefore, despite the initial cardiovascular stability, after several days of using this treatment, hypotension of unknown origin may occur. The main complication of CVVHD is the increased frequency of bleeding in some patients, whereas in others, there is an increased frequency of thrombosis on the filters (Ronco et al. 2000; Levy et al. 2001; Bellomo et al. 2002; ADQI criteria [http://www.adqi.net]). PERITONEAL DIALYSIS (PD) Peritoneal clearance can be used for patients with: • • • •
Head trauma Cardiovascular instability Infection of peritoneal cavity Babies and small children
The method should be initiated when the serum urea is ⱖ240 mg/dl. However, as the levels of urea increase, PD will be insufficient for the patient’s needs because it cannot clear large amounts of urea. Contraindications for PD are: • Infection of organs that border with the peritoneal cavity • Hypercatabolic patients • Patients who have tissue scarring in the peritoneal cavity from earlier surgical interventions • Patients post-operative with an aneurism of abdominal aorta • Patients with recent intervention in the intestine presenting with scarring of tissues (Teschan et al. 1960; Davenport & Goldsmith 1987; Kjellstrand et al. 1988; Congel & Anderson 1992).
DISCUSSION The treatment of patients with ARF in the ICU is complex. Not only should the mechanical equipment be efficient and technically correct but the psychological state of the patient is also
Indications for RRT in the ICU Indications Description Azotaemia Renal uraemia Neuropathy, myopathy Encephalopathy (unexplained decline in mental status) Pericarditis Volume removal Overload of fluids Pulmonary oedema Oliguria with 1.2 (Kt / V)
IHD (3–4 hours)
?
1.4 (Kt / V)
Table 3: Inferior values of haemodialysis adequacy in ICU.
Table 4: Ideal dose of haemodialysis adequacy in ICU.
It is possible in most cases to prevent ARF in ICU from developing into chronic renal failure if the correct method of treatment is used. Renal recovery is an important measure of outcome in ARF, and thus it becomes quintessential to ascertain if the renal replacement modality has any impact on this outcome measure. CRRT appears to provide less dialysis dependency compared with intermittent dialysis, and a pathophysiological explanation for this observation can be easily found. In a previous paper, the Beginning and Ending Supportive Therapy (BEST) group showed a significantly higher incidence of hypotension in patients receiving IHD (twice as much compared with CRRT) (Shigehiko et al. 2005, Ronco 2007).
neutrophils, macrophages, monocytes and the mechanism of blood coagulation, possibly contributing to an induced delay of renal function recovery..
CONCLUSION Comparing all the above-suggested methods, recent clinical trials (Himmelfarb 2007; Ricci & Ronco 2008) have shown that IHD, as applied in chronic renal failure, causes fluctuation of the intravascular volume and repeated systematic blood pressure declines, aggravating periodically the renal ischaemia and thus delaying the tubular recovery. In addition, the use of bioincompatible membranes activates the complement system,
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Highly catabolic patients may need dialysis on a daily basis (high solute clearance), whereas patients with minimal metabolic disturbances can undergo dialysis on an intermittent (every other day) programme. Until recently, PD was rarely applied (poor solute clearances, limited potential to control hyperkalaemia, risk of peritonitis, low volumes of fluid removal, unpredictable hyperglycaemia, dialysate leak from peritoneal cavity and pressure of the diaphragm, leading to respiratory dysfunction). It requires a trained expert staff and the use of chronic catheters (infraumbilical region of the middle line or on the side line, further away from the inner haunch artery—surgical or peritoneoscopic insertion) and peritoneal solutions identical to the solutions used by CAPD (48–96 litres of peritoneal dialysate/24 h) (Depner 1994). The survival of patients with ARF is related to the prescribed dose of IHD (Kt / V >1.0/session). Patients with ARF who were treated with PD presented the same or and lower mortality in comparison
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to patients under IHD treatment (lower fluctuation of daily body weight, stability of blood pressure, continuous mild fluid overload, with higher mean pulmonary artery pressure [PAP] and constant protein removal from the plasma). The most important complication of PD is peritonitis from St. epidermidis or candida. There is no evidence to confirm which treatment method is most suitable. It depends on the hospital, the personnel and the clinical condition of the patient. PD is appropriate for patients with haemorrhage or haemorrhagic disposition and patients with head trauma. There is no need of anticoagulants because osmotic pressure fluctuations of the plasma are mild or even insignificant. IHD is the best choice for hypercatabolic patients because it ensures sufficient solute clearances. From the CRRT methods, CAVHD is preferred in the management of haemodynamically unstable patients and those who are critically ill, because it barely influences the cardiovascular system. If artificial nutrition is essential, then one of the CRRT methods is necessary.
The epidemiology of severe ARF in the ICU has significantly changed over the past decade to sepsis and septic shock. This has been accompanied by an ongoing evolution in the technology of clearing the blood to offer renal support. Intermittent RRTs and CRRTs are available and have both advantages and disadvantages depending on the individual’s clinical situation. Because a greater survival benefit has not been demon-strated for either method, it is the task of the nephrologist/ intensivist to develop an RRT strategy for each individual patient. From this standpoint, it seems prudent to have different RRT modalities available (Eckardt 2006; Stefan & Eckardt 2007). Although it is demonstrated in this paper that adequate RRT doses result in improved survival rates in patients with ARF, clear guidelines on the dose of RRT and the timing of the initiation of RRT are still lacking. It remains a matter of debate whether patients with sepsis and septic shock benefit from early RRT initiation, the use of increased RRT doses and/or increased removal of mediators.
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