• reduce hemodynamic instability
• reduced possibility of ischemia of renal tubules

Removal of fluid

Removal of solutes

Removal of waste products

Continuous veno-venous hemofiltration

Plasma water and solutes - removed by convection and UF using blood, effluent and replacement pumps

Continuous veno-venous hemodialysis

Diffusion and UF are achieved using the blood, effluent and dialysate pumps.

Continuous veno-venous hemodiafiltration

Convection, diffusion and UF are achieved using blood, dialysate, effluent and replacement pumps.

Hemodynamically unstable ICU patient with 

ARF

severe fluid volume overload

NB: there are also many other indications for CRRT

1. Significant organ oedema (especially lung)
2. Sepsis
3. SIRS
4. MSOF
5. ARDS
6. Fulminant hepatic failure
7. Severe burns
8. Cerebral oedema
9. Tumor lysis syndrome
10. Coagulopathy requiring large amounts of blood products in patients at high risk of developing ARDS or pulmonary oedema
11. Cardiopulmonary bypass
12. Suspected uremic organ involvement (pericarditis)
13. CHF
14. Lactic acidosis
15. Drug overdose with toxin removable by extracorporeal therapy

What is tumor lysis syndrome?

• A group of metabolic complications occuring after cancer treatment (usually lymphomas and leukemias)
• Caused by the breakdown of dying cancer cells
• Results in hyperkalemia, hyperphosphatemia, hyperuricemia, hyperuricosuria, hypocalcemia.
• Leads to acute uric acid neuropathy  (renal tubular obstruction by urate and uric acid crystals; increased tubular pressures) and acute renal failure

Increased BUN (normal 8-20 mg/dL)

Increased creatinine (normal 0.7-1.4 mg/dL)

CRRT allows slow, continuous and adaptable fluid and solute removal over a 24hr period

IHD provides rapid fluid and solute removal over 3-4hr period

Fluid and solute removal is slower, thus reducing risk of hypotensive episodes and allowing management of fluid volume.

IHD has higher risk of hypotensive episodes because of rapid fluid removal.

• Continuous control of electrolytes, pH and uremia
• Optimization of nutritional support with TPN (IHD requires fluid, protein and diet restrictions b/w dialysis sessions)
• Convective therapy allows a wider range of solute clearance (IHD therapy based on diffusion)
• Sterile system as no water hookup required.
• Reduced risk of clotting and subsequent blood loss with smaller filter and circuit
• high velocity blood flow and circuit volume reduce the extracorporeal circuit volume
• Managed by ICU nurses rather than dialysis nurses
• On-screen instructions and 24/7 phone support

• non-sterile dialysate
• stagnant bicarbonate solution
• contamination of fluid compartments
• chlorine exposure

Sustained low-efficiency dialysis

nocturnal dialysis (usually 8-12hrs overnight 6 days a week)

Pressure gradient (hydrostatic pressure) created by the effluent pump forces fluid containing solutes and plasma water across the semipermeable membrane.

SCUF, CVVH, CVVHDF

to a lesser extent CVVHD

The movement of solutes with fluid.

Also called "solvent drag"

Occurs during ultrafiltration.

Convection is the main transport mechanism in CVVH and CVVHDF.

Solutes move from a higher to a lower concentration across the semi-permeable membrane into the dialysate compartment of the filter.

The dialysate flows in the opposite direction to the blood causing continual diffusion of solutes.

CVVHD and CVVHDF

They require a dialysis pump.

Adherance of some molecules to the membrane surface.

eg. inflammatory mediators

ultrafiltration rate or

Quf

Dialysis flow rate or

Qd

Blood flow rate or

Qb

Replacement flow rate or

Qr

Solute molecular size

Semi-permeable membrance pore size

Blood flow rates (?)

<300 daltons

urea, creatinine, sodium

glucose, uric acid, phosphate

potassium, phosphorus

500-5,000 daltons

vitamin B12

5,000-50,000 daltons

LMW proteins - beta2 microglobulins, cytokines, myoglobulin

albumin

inulin

• Infection (contamination of access or equipment
• Vascular access complications related to vascular spasm (bfr too high), movt of catheter against wall of vessel, improper length of catheter
• Fluid volume deficit (excessive fluid removal without adequate replacement)
• Hypotension (volume depletion, cardiac dysfunction, vasoplegic state)
• Electrolyte imbalance (high UF rates/clearance rates, inadequate replenishment of electrolytes (IV) or bicarb
• acid/base imbalance (related to renal dysfunction or respiratory compromise)
• Blood loss (anticoagulation). Ineffective anticoagulation causing filter clotting, disconnection, overcoagulation, blood filter leaks
• Air embolus (leaks, faulty connections, hairline cracks on catheter, unarmed or malfunctioning air detector, line separation)
• Reaction to AN69 hemofilter (reaction

medical history (past and present)

current medications

relevant lab data

mentation

orientation to person, place and time

ability to communicate

ICP if being used

function of cranial nerves

deep tendon reflexes of extremities

mobility/immobility

bilateral muscle strength

use of sedative/anesthetic agents, muscle relaxants or paralytic agents

heart sounds - gallop, S4 S3, pericardial friction rub

blood pressure

baseline ECG, heart rate and rhythm

apical/radial pulses and peripheral pulses (presence and strength)

edema - location and amount

hemodynamic parameters - CVP, PAWP, PAD, CO, CI SV EF

core temperature

current cardiac medications/infusions, vasopressors

IABP

temporary or permanent pacemaker

ventricular assest device

cardiac reports (echo)

breath sounds and respiratory effort

CXR - presence/absence of pleural effusions, CHF, ARDS, pneumonia, pneumo etc

oxygenation status and baseline ABG

oxygen deliver system

if ventilated - mode and settings

ECMO - extracorporeal membrance oxygenator

bronchoscopy report if available

bowel sounds X four quadrants

bowel patterns - diarrhoea, incontinence, etc

presence of nasogastric, oral gastric or small bore feeding tube

nutritional status - oral, tube feeds, parenteral nutrition etc

diagnostic reports if available (endoscopy or proctoscopy)

fluid volume status - intake and output

weight - preadmission and current

etiology of renal failure - acute vs chronic

presence of foley

types and rates of fluids administered

types and amount of fluid loss from alternate sources - ie. chest drains, ng tube, wound drains, foley, stool, insensible losses

mucous membranes

electrolyte and acid-base balances

diagnostic renal studies - ie. ultrasound

presence of surgical or trauma wounds, scars

skin integrity - presence of ulcers, rashes, ecchymosis, hematomas, induration, erythema

skin colour, temperature and turgor

presence and patency of IV and/or intrarterial catheters

presence of known HIV, VRE, MRSA, Hep A, B, or C

diagnostic cultures/lab reports

current antibiotic administration

patient/family understanding of current illness and past medical illness

available support systems, religious affiliations

patient/family past effective coping mechanisms

patient/family teaching of CRRT therapy

Replacement pump

delivers replacement solution into the blood flow path

maximum 8000ml/hr

occlusive

peristaltic

conveys the blood through the flowpath of the set and back to the patient

Current patient fluid removal rate

Pre blood pump rate

Replacement rate

Dialysate rate

Delivers sterile infusion solution into the blood access line before the blood pump

for anticoagulation and predilution

Flow rate depends on the therapy and set being used

Flow rate 500-4000ml/hr

Left to right:

Effluent - yellowcircle

Pre Blood Pump - white triangle

Dialysate - green square

Replacement - purple hexagon

Connects to the return line before the aeration chamber

Must be connected during setup

Fluid overload

Electrolyte imbalances (K+)

ARF

Normal range: -50 to -150mmHg

Limits: -250 to +300mmHg

Normal range: +100 to +250mmHg

Limits: -50 to +450mmHg

Normal range: =50 to =150mmHg

Limits: -50 to +350mmHg

Normal range: -150 to +150mmHg

Limits: -350 to +350mmHg

What is the Filter Pressure Drop?

How is it measured?

Used to assess the condition of the hollow fibres of the filter (for micro clots).

Measures the pressure difference between the top and the bottom of the filter.

Filter pressure minus return pressure