SUMMARY. Continuous elimination methods are part of complex therapeutic methods used in critically ill patients after burn injuries. We have been using CVVH (continual vane -venous hemofiltration) in our center since 1995.
We use CVVH in patients after burn injury who present with systemic inflammatory syndrome multiorgan dysfunction or multiorgan failure. From 1995 till 2001, elimination was performed under the supervision of an intensive care unit nephrologist. In recent years we have provided CVVH to burn patients independently.
A nurse places sets in the device, flushes the sets with saline with heparine and subsequently drains this off into a collecting bag. After the device is tested it is ready to be used on a patient. The nurse calls a MD and under his supervision begins the elimination.
Elimination parameters are set by the attending MD, and the nurse has a full written record of this throughout the elimination. The MD is informed of any complications during the elimination If an alarm goes off the nurse initiates correction in co-operation with the MD During the whole procedure the patient is clinically observed, and changes of his status are noted in a shock record and elimination protocol.
Since 1995. 60 eliminations have been performed, occupying a total time of 7,400 hours. The work is very demanding and interesting: the patient's status improves significantly.
Key words: CVVH, nursing diagnoses, elimination
In our Burn Center, CVVH (continual veno-venous hemofiltration) has been performed since 1995. Until 2001 elimination was performed under the supervision of an intensive care nephrologist. Since the device ADM OA was purchased for our department we have managed to operate it independently. Since 2005, 60 eliminations have been performed. taking a total time of 7.400 hours. Continual dialysis replaces renal function and is used for blood filtration in patients with acute renal failure who are in a critical condition. Patients indicated for these methods are treated continuously for days. There are several methods that differ from each other in terms of solute removal and vascular access. (I)
Blood filtering is based on three physical and chemical principles: DIFFUSION. FILTRATION (CONVECTION), and ADSORPTION.
Diffusion is defined as a spontaneous process of passive transportation of a substance from an em ironment with higher density to an environment with smaller density. Diffusion takes place on a semipermeable membrane until the concentration of a substance is equal on both sides. The speed of diffusion depends on the concentralion of a solution on both sides of the membrane. on molecule weight, and on the permeability of the membrane (i. e. on the size of pores and the thickness).
Filtration is a phenomenon during which solution passes through a membrane as well as the substance dissolved in it. The impelling power of filtration is the pressure gradient on the membrane. This means that water transfers from an area with higher pressure to an area with lower pressure, transporting solutes with it.
Adsorption plays an important role in blood cleansing. Only solutes with a molecule, weight not exceeding the permeability of a membrane can cross it. Solutes with greater molecule weight are retained by the membrane. The membrane with tire absorbed substances becomes less permeable for substances transferred by diffusion or filtration.
During CV VH blood is transferred to and from the veins. The impelling power for the blood is a pump, which also ensures the steady flow of the blood. Steady flow is important for effective cleaning and for prevention of blood coagulation in the filter. A blood flow rate of 200 ml per hour allows for ultrafiltration and clearance of up to 30 litres of urea per hour. Ultr afiltrate is of course substituted - the extent of substitution depends on hydration of the patient.
Substitute solutions are supplied by manufactures in sterile bags. Their composition responds to the extracellular fluid. In our patients we use these substitute solutions during elimination:
The decisive factors for the use of substitute solution are the main laboratory results of the patient. The levels of sodium, potassium, calcium, magnesium, chloride, lactate, bicarbonate, and glucose are important.
Capillaries (haernofilters) are designed as hollow fibers with a low resistance to blood perfusion, high ultrafiltration coefficient and minimal tendency to blood clotting. Membranes are made of biocompatible materials. According to the ability to the ultrafiltration, capillaries are divided into low-flux and high-flux.
Patients indicated for therapy by elimination method often have various disorders of the haemostasis. These disorders develop as a consequence of unpaired renal and liver function due to sepsis or other causes; the patients have undergone surgery or trauma, or have catheters inserted, etc. The dialysis membrane and other parts of the haemodiatysis are trombogenous and require antithrombotics. It is not surprising that during elimination there is a danger of bleeding as well as thrombosis in the dialysis. Moreover, despite all efforts bleeding and thrombosis are the most common complications during the use of elimination methods.
Extracorporcal circulation is washed with saline with heparin prior to the procedure. Heparinization must be individualized based on routine laboratory tests.
In our department we use anticoagulation with highmolecular and low-molecular heparin (Fraxiparine, Clexane). To unbind the heparin we use 1% Protamin sulfate (we connect it behind the capillary). If the patient suffers heavy bleeding, we perform the elimination without heparin.
Good quality of vascular access is one of the basic conditions for successful treatment. Suitable access routes are the femoral vein, internal jugular vein. and subclavian vein. One catheter with a double lumen or two catheters with one lumen are inserted. Catheters are made of various materials; polyurethane, silicone, and polytetrafuoroethylene.
Nurses assist during insertion of the catheter and treat the area of the catheter insertion according to standard procedures (disinfection. powder - Framykoin, fixation, coverage and aseptic access).
Indication for CV VH in severely burned patients
a) Renal- renal acrd liver failure:
b) Non-renal - sepsis with multiorgan dysfuction syndrome:
Device description, operation
In the upper left part of the device there are three presoutputs - arterial, venous, and ultrafiltration. The fourth output for the transmembrane pressure can be found on the left side. On the 1c11 hand side three pumps are located: arterial. for substitution. for filtrate. On the right hand aide there is an air detector, venous valve plus optical detector (under the air detector) and detector of blood leakage. In the lower middle part of the device there are two weights distinguished by colour (blue = substitution. yellow = filtrate). On the right hand side from the weights is a heater for the backup. (Fig. 1, 2.)
<% immagine "Fig. 1","gr0000001.jpg","Fresenius ADM 08 after starting inserting",230 %> <% immagine "Fig. 1","gr0000002.jpg","Fresenius ADM 08 after starting the procedure",230 %>A nurse places the sets into the device, flushes the sets with saline with heparin (20,000 units of heparin for 2 liters of saline) followed by unbinding outside the patient. If flushing of the sets runs without complications, the device is ready to he connected to the patient. A nurse calls a MD and under his supervision connects the Quint catheter. The MD sets the parameters on the device (ultrafiltration, exchange, speed of the blood pump. and temperature). In the beginning of elimination it is necessary to extend pressure limits of alarm. Pressure can significantly decrease during the connection.
A nurse records process of elimination. Physiological functions (blood pressure, pulse rate, saturation of oxy- body temperature. central venous pressure, arterial pressure, hourly fluid balance) are followed hourly. Values are then recorded into a shock record for the patient. A nurse also performs blood collection according to MD orders and provides for other needs of the patient (blood count, plasma and urine osmolality glycemia, ions, urea, creatinine, albumin. lactate, acid-base ratio, haernocoagulation plus AT III, anti X A).
Nursing diagnoses
Dehydration caused by continual removal of mater from the organism. By regular monitoring and recording of the hourly dim-esis, enteral and parenteral intake and amount of ultrafiltration we can maintain fluid balance.
Hyperhydratinn due to a device error. We take the same measures as in point 1.
Possibility of blood loss due to leakage of the set of a capillary rupture. We perform regular leak test of all joints.
Possibility of body temperature change - hypothermia due to connection to the exit-acotporeal system. In the majority of cases body temperature decreases after connection to the extracorporeal system. We monitor body temperature continually. According to the finding we take these measures: set the temperature of the substitution sample to a highcr temperature. wrap the haemofilcapillary in a thermal insulation. and place a source of heat to the ambient environment.
Possibility of bleeding due to anticoagulation therapy.
Every six hours we draw blood for evaluation of haemo- we monitor any possible bleeding. According to the results of the haernocoagulation evaluation a MD adjusts the anticoagulation therapy.
Possibility of catheter sepsis due to an infection in the organism. Quint catheter is used only for elimination. Three times a day we perform dressing change under strict aseptic conditions.
Possibility, of skin breakdown due to limited positioning of the patient during elimination. Prior to initiation of elimination we place the patient on an antidecubital air mattress. During elimination. cleaning and changing bed linen is performed with the help of other nursing team members. While washing we thoroughly treat and monitor whether decubiti are not developing.
The work of a nurse during elimination methods consists of the preparation of an artificial kidney -placement of the sets, testing of the device and flushing of the sets. With the assistance of a MD we connect the device to the Quint catheter.
We consider this method very beneficial in patients with extensive burn injuries with the above listed indications.
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