RRT IN CRITICALLY ILL When?

How?How much?

A 43 year old male presented to emergency department with confusion

History Recurrent attacks of difficulty in passing

urine , urine volume was decreasing over the last month together with sever burning sensation.

Recurrent attacks of fever during the last 2 weeks with incomplete antibiotic courses.

History of acute lumbar disc prolapse with severe back ache & heavy use of analgesics ( diclofenac, ketorlac, feldine……) over the last 3 months.

On examination

Vitals: BP 80/50 mmHg HR 135 bpm, regular Temp. 35˚C RR 30/ min. Cold ,pale peripheral extremities Delayed capillary filling Weak peripheral pulsations Chest exam.: Bilateral harsh vesicular breathing bilateral fine basal crepetation Pupils equal medium size & reactive No lateralizing manifestation Patient is confused, not cooperative, not communicating

Laboratory data

Complete blood count (CBC)  Hemoglobin (g/dl) 10.5 Hematocrit (%) 29 Platelet count 86,000 WBC (cells/ml) 20,000 Segmented neutrophils

85% Band forms

10% 

Chemistry BUN (mg/dl) 60 Creatinine (mg/dl) 7.5 Lactic acid  (meq/L) 7 Potassium (mEq/L ) 5.9 Sodium(mEq/L) 132 Magnesium (mEq/L) 3 Phosphorous (mg/dL) 4.5

Arterial Blood Gases   pH 7.27 pCO2 30

pO2 58

HCO3 15

O2 Sat % 93

Urine analysisLeukocytes 100 HPFNitrite +ve

Imaging CXR hilar congestive

shadow Renal US Normal appearance

What is your diagnosis?

What is your first line of treatment?

What further investigation would you like to request?

would you like to consult other specialty(s)?

Management

Patient admitted to ICU & put on mechanical ventilation

Central line was inserted, CVP measured, it was 12 cm H2O. IV crystalloid was initiated guided by CVP

Arterial line was inserted & invasive blood pressure was monitored. BP was 75/40mmHg

Noradrenalin infusion was started at rate of 150 nanogram /kg/ min.

Foly’s catheter was inserted , only 20 ml of urine was there

Anti biotic was started empirically based on Antibiotic protocol for treatment of community acquired UTI ( 4th generation Cephalosporin started with renal adjustment of the dose)

Sepsis screening done as blood & urine culture was send to microbiology lab.

Would you initiate any RRT for this patient?

Why?

What type of RRT would you use?

Nephrologist was consulted & he recommended initiation of CRRT in the form of CVVHDF

CVVHDF was started through RT femoral venous catheter

Forty-eight hours after CRRT was started, patient’s potassium level was 3.5, his creatinine level was 6.3, and his BUN was 57. Potassium was added to his intravenous fluids and his electrolytes continued to trend toward normal.

After five days of the initiation of antibiotic, patient’s sepsis was slowly resolving and he was weaned from both the ventilator and his vasoactive drips. IV antibiotics were continued until day 14 of hospitalization. patient’s renal function returned and he was discharged from the hospital on day 18

Acute renal failure and renal replacement therapy in

the ICU Acute renal failure (ARF) is a sudden and sustained fall in the glomerular filtration rate (GFR) associated with a loss of excretory function and the accumulation of metabolic waste products and water.

It leads to rising serum urea and creatinine, usually with a fall in urine output.

Up to 10% of all patients admitted to the ICU receive some form of renal replacement therapy.

Types of RRT

RRT classified according to the intended duration of each treatment (intermittent vs continuous) and, in the case of continuous, both the access (arterial vs venous) and the circuit type (dialysis vs filtration).

CRRT usually involves the removal and return of blood through a single cannula placed in a large vein (venovenous therapy), arteriovenous Haemofiltration is of historical interest only.

Intermittent VS

continuous

Venous VS

arterial

Dialysis Vs filtration

When?

Intravascular volume overload unresponsive to diuretic therapy;

Hyperkalemia refractory to medical management.

Severe metabolic acidosis. Persistent oliguria or anuria, unresponsive to

volume administration. Overt uremic symptoms (encephalopathy,

pericarditis, bleeding diathesis); and Progressive azotemia in the absence of

specific symptoms.

Important considerations

There is still no generally accepted azotemia threshold for when to start RRT.

A better term is acute kidney support as it is analogous to mechanical ventilatory support;

Therapy should be considered in patients with marked impairment in organ function and not limited to patients with complete failure.

There is consensus that therapy should begin before complications develop.

How? What is renal replacement

therapy? There are two main physical processes

that are employed to carry out the kidneys' function of the removal of solute and water from the body and thereby maintain a steady state:

* Haemofiltration

* Haemodilaysis

Renal replacement systems may rely predominantly on Haemofiltration (convection) or haemodialysis (diffusion) but there are also systems that combine the two methods.

Haemofiltration process

Convection describes a process by which solutes are transported across a semipermeable membrane together with the solvent by means of filtration driven by a trans-membrane pressure gradient

Convection removes middle molecular weight proteins of 5000–50,000 Da.

The transmembrane pressure existing from one side of the hemofilter to the other leads to the passage of solvent (plasma water), bringing with it the passive flow of solutes it contains.

Many of the septic mediators (e.g. cytokines, complement) lie within this group. These mediators are absorbed onto the filter membrane and so removed.

Interest surrounds the use of high volume Haemofiltration to remove these inflammatory mediators to improve outcome from severe sepsis.

High volume filtration is defined as ultrafiltration of over than 2 liters/hour, and there is evidence that filtrate volumes up to 6 liters/hour are associated with a significantly lower mortality in septic patients.

Haemodialysis process

Diffusion describes a process passive transport of solute across a semi-permeable membrane driven by a concentration gradient such that the solute will tend to an equal concentration in the available distribution space on both sides of the membrane ( from blood to dialysate)

Blood flow and dialysate flow rates are set in order to obtain the best compromise between maximum diffusion and good hemodynamic tolerance.

The conventional dialysate flow rate is about 500 mL/min

and the blood flow rate is about 300 to 500 mL/min.

Diagram of a haemodialysis circuit. In green: dialysate. In yellow: used dialysate.

Hemodialysis allows the passage of small molecules (with molecular weights of 500 to 5,000 Da) from blood to dialysate.

Therefore, it allows the removal of many metabolic waste products and can maintain good electrolytic homeostasis.

The main side effect of IHD is the possibility of poor hemodynamic tolerance

Sustained, low-efficiency dialysis (SLED) and continuous haemodialysis are sub-modalities in which the duration of dialysis is extended (6 to 12 h or even 24 h), allowing for more gradual removal of solutes and fluid and hence better hemodynamic tolerance.

Diagram of continuous Haemofiltration. In yellow: ultrafiltrate. In pink: replacement fluid (post dilution).

Diagram of continuous heamodiafiltration. In green: dialysate. In pink: replacement fluid (postdilution). In yellow: ultrafiltrate plus used dialysate

Haemodiafilteration

Why CRRT?

Reduces hemodynamic instability preventing secondary ischemia

Acid base balance Electrolyte management Allows for improved provision of

nutritional support Management of sepsis/plasma cytokine

filter Safer for patients with head injuries Probable advantage in terms of renal

recovery

Intermittent Vs continuous

How much?

For continuous haemofiltration, intensity can be more readily quantified by the ultrafiltration flow rate, commonly expressed as ml/kg/h of ultrafiltrate. Early results from single-center trials showed that increasing the ultrafiltration rate was associated with improved survival in critically ill patients with AKI.

25 to 30 ml/kg/h be prescribed in the hopes of achieving the 19 and 22 ml/kg/h is recommended

Dose of CRRT

Dose = amount of solute clearance

CRRT = Effluent flow Monitor

Time-averaged serum urea

Dialysis dose: One size does not fit all!

Modifications required based on:

Protein catabolic rate Patient weight Interruptions Recirculation

Complications

Circuit and haemofilter thromboses lead to reduced efficiency of the RRT and possible blood loss.

During a haemodialysis session, back-diffusion can be observed if the transmembrane pressure becomes negative. It means that molecules pass from the dialysate to the blood compartment. It is necessary to provide a minimum ultrafiltration flow rate across the membrane to avoid this phenomenon.

The use of heparin can be responsible for bleeding and heparin-induced thrombocytopenia.

Poor hemodynamic tolerance may occur. The main causes include rapid solute removal (IHD) and hypovolemia induced by the removal of plasma water from the blood compartment. The preservation of a relative hemodynamic stability during the RRT session is probably the most difficult goal to achieve. Recurrent episodes of hypotension must be avoided because they can perpetuate organ injury and likely delay renal recovery.

Numerous complications are linked to the use of the catheter. Depending on the venous site (femoral, subclavian, or internal jugular), complications of catheter insertion include arterial puncture, local bleeding, hematoma, pneumothorax, hemothorax, retroperitoneal bleeding, or cardiac arrhythmia. The use of guided insertion procedures, such as ultrasound, has reduced both the incidence of these complications and the rate of catheter insertion failure. Once inserted, catheters may also result in several mechanical problems (eg, malpositioning), thrombosis, and infections.

Drug removal/dosing

Factors to consider Drug Molecular Weight Volume of distribution Protein binding Ionic charge AN 69 cut-off 56,000 Daltons Solute with a molecular weight > 56,000 will not be

removed Urea= 60 Creatinine=117 Albumin=62 000 Vancomycin=1449

Special Attention

· Close management of laboratory values: Potassium Phosphate Magnesium

· Nutritional assessment due to amino acid and other nutrient losses during CRRT

· Hypothermia

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