 Because each patient is different, physicians make a careful evaluation before writing a prescription for hemodialysis. Selection of the dialyzer, blood flow, actual time delivered, dialysate composition, heparin monitoring, fluid management. These are all components of the dialysis prescription that have to be considered. The provision of an adequate dialysis is the major task of the entire dialysis team. Patient survival is dependent on this. The amount of dialysis given is measured by the urea clearance of the dialyzer delivered over a specific time in a patient with a specific volume. This is expressed as KT over V, which is measured regularly. An alternative to the use of KT over V is the urea reduction ratio, or URR, which is calculated by pre-dialysis BUN minus post-dialysis BUN over pre-dialysis BUN times 100. As the patient care provider, you must always supply a certain quantity of dialysis. The physician has carefully determined what that quantity of dialysis should be. The delivery of that prescription is your responsibility. The dialyzer used can reflect the patient's size to a certain extent, and the other option obviously is whether to use a conventional dialyzer or a high-flux dialyzer. The first important element of the hemodialysis prescription is the selection of the dialyzer. The dialyzer has two primary functions. The first is to remove toxins from the patient's blood. This is known as clearance. Clearance is defined as the amount of blood that is completely cleared of a particular solute in a given period of time. It is expressed in milliliters per minute. Usually the clearance of urea is used as the measure of the efficacy of a dialyzer. The dialyzer's second function is to remove water from the patient, a process called ultrafiltration. Ultrafiltration is the transfer of fluid between the blood and dialysate through the dialysis membrane due to a pressure gradient existing between the blood and dialysate compartments. The physician has taken a number of factors into account when prescribing a particular dialyzer, whether high-flux or conventional. These include membrane type, biocompatibility, surface area, clearance of various solutes, ultrafiltration coefficient, priming volume, reusability and cost. If dialysers are reprocessed, you must ensure that patients receive their own dialysers. The decision of the medical director to reprocess dialysers carries with it additional responsibilities for monitoring the delivery of the prescription. Every dialyzer must be properly primed according to the manufacturer's instructions and your facility's protocol to assure that all air, residual disinfectants or manufacturing residues are removed. Another important factor is assuring that the dialyzer has been connected properly to the blood and dialysate lines. To maximize solute clearance, the dialysate flow must be countercurrent to the blood flow. The dialysate flow through the dialyzer is directed upward during dialysis to prevent the accumulation of air bubbles on the dialysate side. When air bubbles are present, the membrane does not come in contact with the dialysate. Diffusion cannot take place and the efficiency of the treatment is decreased. Blood flow and dialysate flow must be set according to the physician's prescription to achieve the expected dialyzer clearances. All machines have a preset dialysate flow rate that cannot be adjusted. Your facility's quality assurance must make certain that the prescribed dialysers are being used, that the blood and dialysate flows are accurate, and that reprocessing is performed according to the AMI recommended practices, federal regulations, and your facility's established procedures. Blood flow is critical. With the kind of dialyses that are being prescribed in the United States in this era, the blood flow that is prescribed must be achieved. Blood flow is an essential component of the prescription since the dialyzer's solute clearance directly correlates with it. Adequate blood flow is dependent on the patient's blood pressure, condition of the access, needle selection, and needle placement. Check the vascular access, visually inspect, palpate for thrill and contour, listen for brewery, and observe for aneurysms. Look for areas of redness or drainage. Evaluate the access for direction of flow and clean and disinfect the access before placing the needle. Make sure that the needle gauge and length are appropriate for the blood flow that you're trying to achieve. Shorter needles with large internal diameters are usually preferable because they minimize resistance. Be sure you have achieved optimal placement of the needle by verifying a flashback of blood in the fistula needle tubing. Tape the needle immediately and check again for blood flow before attaching the blood lines to the corresponding needle. The prescription is based on the assumption that the blood flow is constant throughout dialysis. Try to achieve a constant, steady flow of blood through the dialyzer as quickly as possible. If the prescribed blood flow cannot be maintained throughout the treatment, the dialysis time may need to be extended. When blood flow from the vascular access is inadequate, there may be several causes. The most likely reason may be as simple as poor needle positioning, which may allow the bevel of the needle to rest against the blood vessel wall, restricting blood flow. Sometimes, personal items may obstruct the blood flow, or the patient may have shifted position. At times, even the tubing itself may kink, which could reduce blood flow to a significant degree. Blood pressure should be monitored frequently to assess the patient's condition. A drop in your patient's blood pressure could decrease the flow rate in the access, reducing the blood flow available to the extracorporeal circuit. If there is a pre-pump arterial drip chamber, observe the flow into the chamber at the initiation of dialysis, and again with each monitoring check of the patient and the equipment. This can be used as a good indicator of blood flow. Some facilities monitor the pressure with a pre- or post-pump arterial drip chamber. Other facilities may use a pressure pillow, and still other facilities may not measure the arterial pressure at all. When the pressure pillow collapses, or a high pre-pump negative pressure is measured, the patient's access is not providing the blood flow rate indicated by the blood pump setting. Patients should not be dialized at pre-pump negative pressures greater than minus 250 millimeters of mercury. High negative arterial pressures are associated with recirculation, blood cell damage, access damage, reduced blood flow, and small air bubbles in the extracorporeal circuit. High negative pre-pump arterial pressures that are not typical for a particular patient at the prescribed blood flow rates should be investigated. Whenever the blood flow from the patient to the dialyzer is reduced, the staff must take immediate action to determine the cause of the problem and do whatever is necessary to correct it. If the negative arterial pressure is not correctable by repositioning the patient's limb or the blood lines, the blood flow rate may have to be turned down or turned off if necessary in order to reposition the fistula needle or recanulate the access. If it is not possible to restore the blood flow to the prescribed level, the physician should be notified and a decision made whether to extend the patient's treatment time. Potential failure of the patient's vascular access can be indicated by greater difficulty in achieving prescribed blood flows, greater negative pre-pump arterial pressures, or gradually increasing venous pressure. Since these signs of impending access failure progress slowly over time, you should review your patient's previous treatment records to evaluate trends which indicate the possibility of access problems. If there are repeated problems achieving the patient's prescribed blood flow rates, it should be brought to the attention of the physician. Another frequent problem is recirculation of blood through the patient's access. Recirculation causes the effective clearances to be reduced. Recirculation may be caused by a partially occluded access or by improperly placed needles. This could include being placed too close together, pointing in the wrong direction, or actually reversing the arterial and venous connections. Recirculation studies should be performed to evaluate whether or not an access is failing. Some small amount of recirculation may be unavoidable and acceptable as long as the prescription takes this into account. In patients with fistulas or grafts, the patient's blood occasionally may appear darker than usual when recirculation is present. Blood routinely appears darker in patients with femoral or subclavian catheters because the catheters are inserted in veins, so the color of the blood is not always a good indicator of recirculation. Remember that dual lumen venous catheters are particularly susceptible to recirculation because the arterial and venous openings are so close together. It is not good practice to reverse the bloodlines to improve blood flow. This can greatly increase recirculation and could affect the dialysis prescription. Recirculation is far more common than many clinicians realize and should be suspected whenever the KT over V or URR results are lower than expected for the prescribed dialysis. Your facility's quality assurance must see to it that prescribed blood flows are being maintained throughout the treatment. It is important to monitor routine calibration of blood pumps and machine pressure gauges. It should also include observation of staff for compliance with facility procedures and in-servicing as needed. Even in the hospital environment, we would tend to concentrate on the time of treatment as being the critical factor. This is a little old-fashioned, but results in Europe have often shown this to be justified. The actual time delivered is a critical component of the dialysis prescription. This involves both the frequency of the dialysis treatments, how many times per week the patient comes in for treatment, and the length of time prescribed for each treatment. Simply noting the elapsed time from the start of dialysis to its conclusion may not be sufficient. If you analyze a patient's prescribed time compared to the actual treatment time, you may find that a significant number of treatments were shorter than prescribed. This raises concerns that the high mortality rate and morbidity of dialysis patients may be due to less than adequate dialysis prescriptions or treatment delivery. The most effective way to determine actual dialysis time is with the use of a machine clock that runs only when dialysis is taking place. Some machines visually display this number. The clock will not run when there are machine alarm conditions that cause an interruption in blood or dialysate flow. If machine clocks are not available, you should note the amount of time that the dialysis is not being delivered. Additional time should be added to the treatment to compensate for the interruptions. The shorter the prescribed treatment time, the more critical this becomes. There are many reasons for the dialysis treatment to be interrupted and you may have little or no control over these conditions. For example, if the patient moves and kinks the lines, this may result in an alarm condition that stops dialysis. Dialysis will also be interrupted if the temperature of the dialysate is out of limits, if there is a blood leak, if there is a pressure excursion beyond the set limits, or if the conductivity of the dialysate is either too high or too low. Any of these interruptions will decrease the actual time that the patient is dialysed. Richard, you have a taxi cab waiting for you downstairs. Occasionally, dialysis may have to be interrupted or terminated for medical, personal or other reasons. If this occurs, you must document these situations and when or if treatment resumed. You should remind your patients that they have a responsibility to arrive on time and to remain for the specified length of treatment. It's never acceptable to deliberately shorten the actual time of a patient's dialysis, either for your own or the staff's convenience. Surveys have shown that treatments are sometimes shortened at the end of the day or when facilities are closing for the weekend. There may be a tendency to take shortcuts knowing that your patient will return in a couple of days and that you can make up the lost time. However, making up lost time is not always possible. If treatment time is shorter than prescribed, the patient could develop serious complications. Therefore, a careful study of the actual dialysis treatment times should be a part of your facility's quality assurance process. A study of dialysis treatment times would include observing staff practices, auditing records to assure compliance, assuring the time is being measured and recorded accurately, and that interruptions of blood flow and or dialysate flow are noted and factored into the total time of dialysis. The outcome of a quality assurance process should be to consider these actions. Educating your facility's staff on the importance of dialysis treatment time, educating your patients in regard to their role, and when necessary, having the physician reevaluate the dialysis prescription. All patients expect and deserve the treatment specified in the prescription. It must be delivered consistently, accurately, and for the time required. When we decide the dialysis fluid composition, the purpose is of course to purify the uremic blood and to normalize the composition of blood, and we select the composition to do the job properly. Another important component of the dialysis prescription is the dialysate composition. The function of the dialysate is to balance the chemical composition of the body fluids. Failing to provide the prescribed dialysate can have serious adverse effects for the patient. First you must assure that the prescribed formula and type of concentrate are used. It is essential that the acid component of bicarbonate dialysate concentrate not be confused with the acetate concentrate or with the bicarbonate concentrate. It is critical that you take the time to read the labels on these containers. Use water that meets the AMI standard when mixing the powdered sodium bicarbonate into a liquid. The water should be at room temperature for the best mix with the sodium bicarbonate. Never shake the container as this releases the carbon dioxide. Remember the mixed bicarbonate dialysate should be discarded after 24 hours because of the risk of potential bacteria growth. For patients who need additives, you must verify that the appropriate additive formulation is prepared. It is also important to verify that the amount of additive used is appropriate to the dilution ratio of the concentrate and the volume of the concentrate container. Clearly label the container with the formulation, the date and time of preparation and the initials of the preparer. Make sure that the powder is completely dissolved. You must begin each session with enough concentrate to complete the entire treatment. The machine settings must be verified as correct for the dialysate prescribed for your patient. If the machine is equipped with a variable sodium option, it should be set for the prescribed dialysate sodium level. Also, if the dialysate flow rate can be adjusted on the machine, make sure that it is set as prescribed. It is the physician's role to prescribe the dialysate composition. It is your role to make sure that prescription is carried out. Remember that the dialysate chemical composition is equivalent to a medication with the same potential for harm to the patient. The general rule is to check and double check, then check again. It is essential that your facility have adequate quality assurance procedures to make certain that the dialysate is consistent with the prescription. This is accomplished by ensuring that the proper mixing of concentrate takes place. The necessary machine safety checks are performed prior to treatment. Routine or periodic preventive maintenance is completed and that adequate patient and machine monitoring are performed during treatment. The biggest problem with heparin in a maintenance unit is that individual patients' heparin requirements change from time to time, particularly as the seasons change. So it's necessary to monitor the effects of heparin so that you don't over-heparinize or under-heparinize. Heparin is the most common anticoagulant used in hemodialysis. The use of heparin prevents clotting of the extracorporeal circuit, including the dialyzer. Clotting is a serious problem because it causes a reduction in the available membrane surface area. This reduces the effectiveness of the dialyzer so that the prescribed amount of dialysis cannot be delivered. If partially clotted, the dialyzer clears fewer toxins and this results in reduced KT over V or URR if not recognized and corrected. Careful assessment of your patient's anticoagulation requirements is critical. Ongoing clotting studies should be done according to unit protocol to monitor the adequacy of heparinization. The anticoagulant can be given to your patient in a single systemic dose at the beginning of the dialysis treatment, or it can be given continuously with the use of an infusion pump or intermittently during the treatment following an initial bolus. With syringe pumps, verify that the correct syringe size is being used and that it has been loaded into the infusion pump according to the manufacturer's instructions. Each time you check your patient, you should record the dose of heparin that has been delivered. Choosing the wrong size syringe, failure to prime the heparin line or to turn on the heparin pump may cause an improper dose of heparin to be delivered. If there is concern about the dose delivered to the patient, the calibration of the infusion pump should be checked. If your patient suddenly shows unusual clotting characteristics, you should initiate actions to alleviate the problem. Talk to the patient and determine if there have been any unusual medical problems since the last treatment. Patients with an infection or fever often require an increased heparin dose to prevent dialyzer clotting. Sudden, isolated clotting episodes can occur in patients without acute illness and despite seemingly adequate anticoagulation. Other factors that can affect heparin requirements include drugs such as aspirin and other antiplatelet agents, warfarin and other anticoagulants, nicotine, digitalis, tetracycline and antihistamines, medical conditions including fever, infection, uremia, thrombophlebitis, myocardial infarction, cancer and liver disease. Patient characteristics that affect heparin requirements include differences in sensitivity, metabolic and elimination rates and platelet count and for female patients menstrual cycle. Characteristics of the dialysis system also affect heparin requirements including dialyzer configuration and flow geometry, membrane type, duration of dialysis, blood flow rate and blood administration. Inadequate air removal during priming can slow or stop blood flow in the individual dialyzer fibers. When fluid is ultra filtered from blood trapped by the residual air it causes the blood to thicken and eventually clot. This can occur even when heparinization is adequate. Medications like EPO increase the red blood cell production and therefore increase the hematocrit. Patients on EPO may require increased anticoagulation with heparin to prevent clotting of the dialyzer. Poor rinse back of the dialyzer may indicate that there are clotting problems. It is important that each possible cause of clotting be investigated and corrective action taken wherever possible. Frequent communication among all members of the care planning team is necessary to arrive at the best solution for each patient. Your facility's quality assurance should make certain that infusion pumps are being calibrated routinely but staff are adequately trained in anticoagulation procedures and that the therapy is being delivered as prescribed. Fluid management and fluid control becomes a problem and it's best managed by having the patient educated so that they don't gain so much fluid between dialysis. The final key element of the dialysis prescription is the patient's dry weight sometimes called target or ideal weight. Weight reflects the patient's fluid and nutritional status. For adequate fluid removal you must assure that the pre and post dialysis weight measurements are accurate. This accuracy is influenced by what clothing your patient is wearing at both weighings and the position of the patient on the scale. It is important that the patient is always weighed on the same scale pre and post dialysis. In addition the scale should be regularly calibrated. The dry weight itself needs to be reviewed on a regular basis since changes in body fat or muscle mass may affect this value. Also when malnutrition is present dietary protein needs may change. Careful determination of the amount of fluid to be removed during the treatment is very important. This involves compensating for the amount of fluid taken in by your patient during dialysis, the volume of fluid used for rinse back and or priming of the dialyzer, and IV therapy including medications, IDPN, and blood and blood products to be administered during dialysis. There are a number of patient considerations that influence fluid removal. Your patient should be assessed for his state of hydration including presence of edema, elevated or low blood pressure, jugular venous pressure, shortness of breath, and the nature of the breath sounds. After determining the amount of fluid to be removed or ultra filtered you must consider whether the patient can tolerate having this amount removed in the time period prescribed. Since fluid removal affects blood pressure blood pressure should be taken pre and post dialysis both standing and sitting. Blood pressure must be monitored closely during dialysis. Staff should respond quickly to changes in vital signs. Fluid is removed during dialysis by means of transmembrane pressure or TMP for short. TMP is calculated using the ultra filtration coefficient provided by the manufacturer of the dialyzer, the dialysis time, and the amount of fluid to be removed. TMP is set on the machine as either TMP or negative pressure. If your machine requires that negative pressure be entered it is calculated as follows. Negative pressure equals transmembrane pressure minus venous pressure. Many machines have automatic control of the UF rate so the TMP is a monitored function. UF control machines will calculate the hourly ultra filtration rate needed only if the total fluid to be removed and dialysis time are entered. In both cases this must be monitored throughout the treatment and adjusted if the patient's condition changes. If there is an interruption of blood or dialysate flow the ultra filtration plan may need to be modified. Routine equipment safety checks should be performed before every treatment according to the manufacturer's instructions. Your facility's quality assurance should make certain that target weight losses are achieved. This includes a determination that the scales are properly calibrated, that TMP or negative pressure are correctly calculated, that ultra filtration controls are functioning, and that the staff receives training in fluid management. This program was designed to give you a better understanding of the components of a dialysis prescription, how the physician determines what prescription is needed, and most importantly that you, the patient care provider, play a key role. The delivery of the hemodialysis prescription is your responsibility. I think it's very important for the nurse or technician delivering the dialysis to understand what we're doing, why we're doing it, and to be aware of the need to follow the prescription accurately. Our nurses must be very good at not only carrying out a prescription written by a physician, but also in using their own judgment in, is this something that will meet the need of my patient. It's very important for the staff to know that every aspect of the prescription, such as blood flow, time, and the things we mentioned earlier are critical to a patient receiving adequate dialysis and there could be no shortcuts in the process. I think that the most important thing is that they all work together. The doctors who wrote the prescription, the nurses will deliver the prescription and the patient that will receive the prescription. The three of them must work together. A very good facility really needs to be doing everything right. From properly treating the water that's coming into the facility, mixing the dialysate, maintaining the machines, having well-trained staff to care for the patients, and of course providing excellent dialysis. This is their life and their help and they're very anxious about it and so we should take them seriously as individuals, deal with their anxieties, deal with their individual characteristics, and remember that this is a social interaction as well as a physical and medical one. There is a lot that we can be proud of in dialysis, in that almost every patient who needs it gets treatment. But I think we have a way to go before we maximize the technology we have available and the information we have to make sure that every patient gets an adequate dialysis and that adequate dialysis is delivered reproducibly.