INTRODUCTION Incidence of ARF: – Community: <1% – Hospital 2-7% – ICU 25% Am J Kidney dis 2005;45:614-18
INTRODUCTION Death in ARF is common “50%“ but permanent renal failure is uncommon “ 5%” The Madrid Acute Renal Failure Study Group recorded a 70% mortality in ICU patients compared to a 50% overall mortality. Kidney Int 1998;66(supp):S16 – 24.
DEFINITION ARF is defined as an abrupt and sustained reduction in renal function, occurring over hours or days, sufficient to result in azotaemia. It may occur from a normal or abnormal baseline level of function.
DEFINITION The first consensus definition of ARF has been developed. It is called RIFLE, the initials reflecting the terms Risk, Injury, Failure, Loss and End Stage in relation to kidney function. This is classifying ARF into 3 severity categories( Risk, Injury & Failure) and 2 clinical outcome categories ( Loss & ESRD) Critical Care 2004, 8:R204-R212
GFR Criteria Urine Output CriteriaRisk S. Cr increased 1.5 times < 0.5ml/kg/h for 6hInjury S. Cr increased 2.0 times <0.5ml/kg/h for 12 hFailure S.Cr increased 3.0 times or <0.3ml/kg/h for 24h Cr = 355 umol/L or anuria for 12hLoss Persistent ARF , complete loss of kidneyESRD ESRD for longer than 3 months
CAUSESThe most common causes of ARF in ICU:1-Sepsis2-Post-operative(Cardiac & Vascular surgery)3-Rhabdomyolysis4-Liver diseases5-Thrombotic microangiopathy.5-Drug induced Contrast Nephropathy Osmotic nephropathy Aminoglycosides, Ampheotricin ,etc
ARF: Risk factors for mortality Multi-organ failure Bacterial Sepsis Fungal sepsis Hypotension/vasopressors Ventilatory support Initiation of dialysis late in hospital course Oliguria/anuria: with oliguric ARF, mortality is > 50% compared to < 20% with non-oliguric ARF
Whatever the circumstances, the‘‘development of ARF in the ICU isbad news.’’ Crit Care Clin 19 (2003) 233– 251
In the ICU, the best time totreat renal failure is beforeit occurs.
Best cure is to prevent Have a high index of suspicion for reversible factors - volume depletion, decreasing cardiac function, sepsis, urinary tract obstruction. Be sure patient is well-hydrated when exposing patient to nephrotoxic drugs
Anticipate problems Avoid worsening the ARF: – Adjust medicines for renal insufficiency – Avoid nephrotoxins if possible – Avoid intravascular volume depletion (especially in third-spacing or edematous patients)
PREVENTION Dopamine & ARF – Although it augments renal blood flow and increases urine volume and sodium excretion, this therapy does not alter the course of ARF in critically ill humans – dopamine can precipitate serious cardiovascular and metabolic complications in critically ill patients. – There is no longer a justification for using low-dose dopamine in treating critically ill patients. Critical care Review 2003
PREVENTION DIURETICS & ARF – In patients with sustained oliguria despite high doses of loop diuretics, this treatment should be withdrawn. – In responders, continuous infusions are preferred because they are more effective and associated with less toxicity than bolus administrations.
PREVENTION DIURETICS & ARF – Mehta showed that diuretic use in ICU patients with ARF was associated with greater in- hospital mortality and non recovery of renal function. – high-dose loop diuretics should be used cautiously in critically ill patients with ARF. JAMA 288:2547-2553, 2002
PREVENTION Aggressive hydration, minimizing nephrotoxins, and maintenance of "adequate" mean arterial pressure remain the main non - pharmacologic strategies to prevent ARF in the ICU. Recentdata suggest that N-acetylcysteine may reduce the incidence of ARF secondary to radio-contrast agents. Crit Care Clin. 2005 Apr;21(2):281-9.
Potential Errors in Fluid Management in the Patient with or at Risk of ARF Insufficient fluid administration: In the oliguric patient one may be afraid of inducing lung edema with excessive fluid administration, so that fluid restriction is often adopted, but while limiting edema formation, this can maintain kidney hypoperfusion and worsen renal function.
Excessive use of diuretics: It may be an attractive option to maintain urine output with diuretics. Actually, from a conceptual point of view, diuretics could decrease the oxygen demand of the renal tubules by inhibiting the Na+-K+-Cl– pump. The major risk with use of diuretics is inducing hypovolemia if diuretics are given in the absence of hypervolemia.
Excess fluid administration: All too often, fluid is given to oliguric patients without sufficient monitoring or without careful attention to which variables are being monitored, with the focus being only on urine output. CVP monitoring in some patients is mandatory.
meta-analysis of studies also suggested an increased risk of temporary deafness and tinnitus with use of high doses of furosemide ,an effect that is often under-recognized . Ho KM, Sheridan DJ (2007). The key indication for diuretics in patients with acute renal failure is hypervolemia, and rather than being used routinely in all patients, diuretics should be restricted to those with fluid overload.
Tips about Types of fluids to be used in ARF Among the colloids, the use of human albumin has been decreasing following several studies and meta-analyses that failed to demonstrate its superiority over other colloids in addition to its high costs .Vincent JL, Sakr Y, Sprung CL, et al (2006) Several synthetic colloid solutions exist, but none is ideal. Gelatin solutions have a relatively low molecular weight (MW) and as such have a limited effect on volume expansion with limited oncotic effects and relatively short (2–3 h) intravascular persistence
Their superiority over crystalloids in terms of volume expansion is, therefore, restricted. Moreover, gelatin solutions can induce anaphylactic reactions, although they are usually transient and of limited severity, and they may compromise clot formation - although to a lesser degree than some of the other colloids (Niemi TT, Kuitunen AH (2005)
Dextrans are mixtures of glucose polymers synthesized by the bacteria Leuconostoc mesenteroides. Dextran 70 (MW 70,000 Da) has been the most widely used dextran for fluid therapy. Although they are efficient volume expanders, dextran solutions are associated with a substantial risk of anaphylactic reaction, even when hapten prophylaxis is given, and also have antihemostatic effects.
A recent study reported that therapy of septic patients with a particular HES 10% solution (200/0.5) was associated with higher rates of acute renal failure and renal replacement therapy than was Ringer’s lactate solution Brunkhorst FM, Engel C, Bloos F, et al (2008) Newer forms of HES may have fewer adverse effects on renal function, but until more data are available, they should be used with caution in patients with, or at risk of, acute renal failure.
Dextran solutions may also precipitate renal failure by accumulation of the molecule in the renal tubules and/or hyperviscosity. The development of hydroxyethyl starches (HESs) was met with some excitement in the hope that these fluids would prove effective without adverse effects.
MANAGEMENT Patients with stable isolated ARF and no evidence of volume overload or gross electrolyte and acid-base disturbance can often be managed conservatively without RRT. Recent studies suggest that unnecessary dialysis itself may delay recovery of renal function. Kidney Int 1998;54:1817– 31.
MANAGEMENT Indications of Dialysis in ARF: – Uremic symptoms. – Uremic pericarditis. – Volume overload. – Hyperkalaemia. – Metabolic acidosis. – Other electrolyte abnormalities.
MANAGEMENT Common wisdom is to start RRT in patients with ARF before azotemic solutes cause clinical symptoms. RRT needs of the ICU ARF patient vary from patient to patient and cannot be considered a single problem solved by a single RRT prescription.
Continuous VS. Intermittent Therapy in ARFDespite the widespread use of CRRT in critically illpatients with ARF, there are few data supporting itsbenefits over conventional (IHD)Despite greater volume control, CVVHD did not leadto improvement in survival, preservation of urineoutput, or renal recovery compared with IHD inpatients with ARF Augustine et al. Am J Kidney Dis. 2004; 44: 6
Reasons for Using CRRT Mehta and Letter: Am J Nephrol 1999; 19:377-382
Advantages of using CRRTSuitable for hemodynamically unstable patientsPrecise volume controlEffective control of uremia, ↑ PO4 & ↑ K+
Advantages of using CRRTRapid control of metabolic acidosisImproved nutritional support (full protein diet)May be an adjuvant therapy in sepsis
Disadvantages of using CRRTExpense – probably the same as IHD Anticoagulation – to prevent extracorporealcircuit from clottingHeparin: Initially 25 IU/Kg, maintenance is by10 IU/Kg/h, to achieve PTT 45-65 sec.
TAKE HOME MESSAGES Acute renal failure is common and is associated with poor outcomes in ICU patients. Adequate intravascular volumes and renal perfusion must be maintained to limit the development of acute renal failure. However, excess volume replacement carries its own risks. We have inadequate tools to assess and monitor fluid balance and responsiveness, especially in patients with capillary leak syndromes, and, currently, carefully conducted, repeated fluid challenges represent the best way of determining ongoing fluid needs.
TAKE HOME MESSAGES ›› Adequate fluid balance and good renal perfusion must be targeted in critically ill patients to reduce the risks of developing acute renal failure. ›› Fluid resuscitation and management are complicated in acute renal failure, and these patients must be carefully and closely monitored. .
TAKE HOME MESSAGES ›› No intravenous fluid is perfect, and fluid choices should be based on individual patient’s requirements. Both hypervolemia and hypovolemia can be detrimental. Diuretic use in patients with acute renal failure should be restricted to patients with hypervolemia. In many patients, it may be wiser to use smaller amounts of several different types of fluid than a large amount of any single solution
TAKE HOME MESSAGES While crystalloids represent a good initial choice of fluid, for large or continuing losses, colloid solutions must also be used. No fluid is ideal, and fluid selection should be individualized depending on specific patient needs and known adverse effects of the different fluid types; in many patients, it may be wiser to infuse smaller amounts of several different types of solution so that the benefits of each type can be maximized while limiting the risks.