Renal Replacement Therapy in Intensive Care Unit for Acute Kidney Injury

AKI occurs in about 30%–50% of patients admitted to the intensive care unit (ICU), about a quarter of whom may need dialysis. AKI patients in ICU differ from ESRD patients on HD in the following ways: (1) the rate as well as the amount of nitrogenous waste products generated is higher due to increased catabolic rate, (2) cardiovascular instability is more likely and (3) there is an increased need for fluid removal and correction of metabolic acidosis. The application of RRT in ICU for AKI should take in to account these factors.

Choice of Renal Replacement Therapy in Intensive Care Unit

1. We recommend that all forms of RRT (HD, SLED, CRRT or peritoneal dialysis [PD]) may be used in ICU.

2. We suggest that adult patients who are septic and hypercatabolic should be treated with HD, SLED or CRRT in preference over PD.

3. We recommend use of CRRT or SLED in patients with hypotension or who require vasopressor drugs.

4. We recommend use of CRRT for patients with increased intracranial pressure such as neurosurgical patients and fulminant hepatic failure. In case CRRT is not available, SLED or PD may be used instead, in such circumstances.

5. The duration and frequency of SLED should be determined by the requirement of UF and need for solute removal.

6. We recommend choosing the modality of CRRT: Continuous venovenous hemofiltration (HF) (CVVH), continuous veno-venous HD (CVVHD), or a combination (continuous venovenous HDF [CVVHDF]), according to clinician expertise and availability of resources.

7. We recommend not using AV techniques of CRRT, as efficacy and safety monitoring may be inadequate.

8. We recommend the use of dedicated machines with full safety features for CRRT.

9. We recommend use of machines capable of low dialysate flow rates (£ 300 ml/min) for SLED.

10. We recommend use of HD or SLED on alternate days. However, more frequent HD or SLED may be done, if metabolic and fluid management demands are not met.

Vascular Access for Dialysis in Intensive Care Unit

1. We recommend the IJV as the preferred vascular access.

2. The vascular access should be a dedicated cannula of a minimum of 12F in adults, and should not be used for administering drugs or TPN or measurement of central venous pressure.

Dialysate and Replacement Fluids

1. We recommend using bicarbonate-based dialysate for intermittent HD (IHD) and SLED

2. We recommend that bicarbonate based dialysate may be preferred over lactate-based dialysate in CRRT

3. We recommend not using lactate-based dialysate for CRRT in patients with liver failure and cachectic patients with poor muscle mass

4. We recommend use of isotonic bicarbonate-based fluid as replacement fluid in CRRT. Alternately, lactate based or saline based isotonic fluids may be for replacement in case isotonic bicarbonate fluids are not available

5. We recommend adjusting the potassium concentrate in the dialysate fluid and replacement fluid between 0 and 4 mmol/L depending on the individual need. Table 1 lists the available fluids which can be used for continuous renal replacement therapy.

Table 1.

Composition of dialysis and replacement fluids for continuous renal replacement therapy

Composition	PrismaSol* (Baxter)	Regiocit**(1) (Baxter)	Dianeal PD*** solution (1.5%)	Prism0Cal***(1) (Baxter)	Biphozyl**(1) (Baxter)	Ringer lactate**	0.9% saline**
Na+ (mmol/L)	140	140	132	140	140	130	154
K+ (mmol/L)	0	0	0	0	4	4	0
Cl− (mmol/L)	109	86	96	106	122	109	154
HCO3− (mmol/L)	32	0	0	32	22	0	0
Ca++ (mmol/L)	1.75	0	1.5	0	0	1.5	0
Mg++ (mmol/L)	0.5	0	0.75	0.5	0.75	0	0
Lactate (mmol/L)	3	0	40	3	0	28	0
Citrate (mmol/L)	0	18	0	0	0	0	0
Glucose (mg/dL)	0	0	1368	0	0	0	0

*Both for dialysis and replacement, **For replacement, ***For dialysis, ¹For regional citrate anticoagulation CRRT. CRRT: Continuous renal replacement therapy

Dialyzers and Hemofilters

1. We suggest that standard IHD and SLED may be carried out with low flux dialyzers

2. We recommend use of dialyzers made of biocompatible materials

3. We recommend use of CRRT sets that are compatible with the machine

4. The UF rate should be adjusted for individual patients

5. The blood flow should be set so that the filtration fraction is <20% of the blood flow (especially applicable to HF and HDF).

Anticoagulation

1. Unless contraindicated, we recommend unfractionated heparin as the anticoagulant of choice during IHD and CRRT

2. We recommend heparin as a continuous infusion inpatients on CRRT with aPTT monitoring every 4–6 h. After an initial loading dose of 1500–2000 units, an infusion of 250–500 U/h may be initiated and adjusted according to the aPTT reports

3. We recommend the aPTT should be maintained at between 45 and 60 s or around 1.5 times the control value

4. We suggest that HD and SLED can be carried out without any anticoagulation in patients with coagulation abnormality or who are at increased risk of bleeding

5. We suggest that regional citrate anticoagulation may be used for CRRT, where expertise to initiate and monitor such a therapy is available.

Initiation and Prescription of Renal Replacement Therapy

1. We recommend that RRT should be initiated emergently when life threatening conditions such as electrolyte disturbances, pulmonary edema or acid base disturbance that do not respond to medical management exist

2. We recommend initiation of RRT electively in AKI, when metabolic and fluid demands far exceed the capacity of the kidney to handle them

3. We recommend a Kt/V of ≥1.2 per session during HD and SLED

4. We suggest increasing the frequency of dialysis to achieve appropriate fluid balance or acidosis, hyperkalemia correction or for urea clearance, if extremely hypercatabolic

5. We recommend that SLED may be performed thrice a week with 6–12 h sessions. More frequent or longer sessions may be determined by the need for UF and acidosis correction rather than enhanced urea clearance

6. We recommend dialysate flow rate of 100–300 ml/min and BFR of 100–150 ml/min during SLED

7. For CRRT, we recommend a total effluent (dialysate plus UF) rate of 20–25 ml/kg/h. However, the dose may be dynamic and adjusted to the metabolic demands of the individual patient. A higher dose may be needed in extremely catabolic or septic patients

8. We recommend combination of diffusion and convection for CRRT, the proportion of which may vary.

Goals of Renal Replacement Therapy

1. We recommend periodic monitoring of blood urea, serum creatinine, serum electrolytes, divalent ions and arterial or venous blood gases while on CRRT. The frequency of tests may be based on the individual needs

2. We recommend the use of standardized protocols to deliver CRRT

3. We recommend achieving volume status as close to euvolemia as possible

4. We recommend correction of acidosis to maintain pH ≥7.2

5. We recommend maintaining serum electrolyte and divalent ion concentrations within reasonably normal limits (sodium: 130–148 mmol/L, potassium: 3.5–5.5 mmol/L, ionised calcium 1–1.3 mmol/L, and serum phosphorus: 2.5–4.5 mg/dL).

Transition of Renal Replacement Therapy Modality and Stopping Renal Replacement Therapy

1. The different modalities of RRT in AKI should be view as complimentary and a switch from one modality of RRT to another may be done, when the specific indication to choose a particular modality no longer exist

2. When patient becomes hemodynamically stable, modality of RRT may be switched from CRRT and SLED to IHD

3. Guidelines for termination of RRT in AKI are unclear and are empiric. An attempt may be made to withdraw RRT if spontaneous urine output is consistently more than 30 ml/min for at least 6–12 h

4. In case a decision to withdraw patients from RRT is made due to the futility of such therapy, it should be taken after much deliberation among all the members of medical care giver team and immediate family members.