The number of patients who start hemodialysis because of chronic renal failure continues to increase, and with this increase the various complications associated with hemodialysis become more and more important as factors that determine a patient’s prognosis. The most frequently seen complication during hemodialysis is hypotension (hemodialysis collapse), the causes of which are reported to relate to: 1) a decrease of blood volume (BV) by water deletion during hemodialysis,1 2) insufficient water refilling from extravascular space for BV decrease, 3) decrease of peripheral vascular resistance due to autonomic nervous system dysfunction,1,2 4) cardiac dysfunction, 5) nitric oxide production,3 and 6) adenosine production.4
Hemodialysis collapse causes the patient to feel ill, with symptoms of nausea and shock, making it mentally and physically difficult to continue the hemodialysis session. As a result, there is a decreased efficiency in the hemodialysis and insufficient water deletion, causing a vicious cycle of increased load for the next session. To prevent these consequences, the patient’s optimal dry weight should be established and any weight gain should be brought to the patient’s attention. In addition, there should be an evaluation of the hemodialysis conditions (extracorporeal ultrafiltration method,1 low-temperature dialysate,5,6 high-Na dialysate,7 biofeedback system,8 and profiled dialysis9) and of the water deletion plan (the change of the water deletion rate based on an evaluation of the change of effective arterial blood volume using crit-line, or thoracic electrical impedance10). When hemodialysis collapse is still inevitable, then water deletion stoppage, infusion (isotonic saline, hypertonic saline,11 human albumin,12 hydroxyethyl starch13), and administration of vasoconstrictor (amezinium,14 midodrine15,16) are performed according to the need. However, when or if infusion is given, at the time of the restart of hemodialysis after BP recovery, the amount of infusion in addition to the originally planned amount of water deletion should be removed. Therefore, due to the potential danger of recurring hemodialysis collapse, it would be difficult to complete a predetermined water deletion plan.
It is known that the venous system in vivo in a state of suddenly decreasing BV, such as hemodialysis collapse, works to increase the venous return by decreasing the total venous capacity and increasing cardiac output attempting to raise BP.17 When isotonic saline is infused at hemodialysis collapse, its volume will be distributed in the extracellular space, theoretically. So finally, about 20–25% of infusion volume remains in the intravascular space.18 As compared with this, when a part of the extracorporeal BV is infused at hemodialysis collapse, all of its volume remains in intravascular space, and it is expected that this method is a very effective treatment for hemodialysis collapse. So we took notice of this action of the venous system and body fluid distribution, and made a charging chamber (C-C). This C-C functions as a venous bubble trap and as the charging volume that was not present previously in order to add the ability to change the volume for extracorporeal blood circulation. We studied the BP recovery effect by artificially increasing the BV in the body by returning the blood from C-C without infusion for hemodialysis collapse.
Materials and Methods
The study included 10 patients (4 males and 6 females) on hemodialysis because of end-stage renal disease, who maintained optimal dry weight without cardiac dysfunction and had hemodialysis collapse episodes (Table 1). Patients’ profiles (hematocrit, albumin, ejection fraction, hemodialysis duration, dry weight, weight gain, and hemodialysis time) are shown in Table 1. All the laboratory data were collected immediately before dialysis was started. The mean age was 66.0 years old. Eight of the patients were diabetic. hemodialysis collapse is defined as exhibiting the following during hemodialysis: 1) a decrease in systolic BP of 30 mm Hg or more compared to the starting BP or systolic BP less than or equal to 100 mm Hg and 2) having shock-like symptoms. Consent was obtained from all patients who were fully informed prior to the study.
The increased volume of the venous line chamber is used as the charging blood volume (Figure 1a). The number of chambers on the venous line was increased to two (connected with tubing), because it was suspected that a single chamber induces difficulty in the charging and discharging maneuvers. The priming volume was 172 ml. BV in the chambers can be increased or decreased by up to 60 ml by injecting or withdrawing air using a syringe (Figure 1b). When dialysis was performed at QB 200 ml/min with the chambers full, the fluid simulation showed that the values of QB flowing through the two tubes connecting the chambers were 124.7 ml/min and 73.6 ml/min (Figure 1c), and there was no fluid stagnation (Figure 1d). All measurements were computed by a Dell dimension 8100 OS WindowsNT computer using CFX TASC flow software. The flowfield was analyzed with general-purpose heat fluid analysis software (CFX TASC flow ver2.10, available commercially). It was assumed that blood was incompressible Newtonian fluid, with specific gravity 1.05, and the viscosity was assumed to be 3 cp. The laminar flow model was used.
Hemodialysis sessions were conducted two or three times per week (bicarbonate dialysate, dialysate flow 500 ml/min, dialysate temperature 36.0ºC, dialysate composition Na 140 mEq/l, K 2.0 mEq/l, Ca 3.0 mEq/l, HCO3 25 mEq/l).
Using an extracorporeal circulation circuit with charging chamber (C-C), we performed priming with the C-C empty, connected the patient and circuit under the usual dialysis conditions, and started dialysis. Ten minutes later, blood pressure was checked for stability. Any air was removed from the chamber using a syringe and the chamber was filled with blood in 5 minutes.
Ten minutes after the chamber was filled with blood, blood pressure and heart rate were measured to confirm that hypotension due to an increase in extracorporeal BV was not induced, and dialysis was continued. When hemodialysis collapse occurred during dialysis, we first elevated the lower extremities, decreased QB (60-80 ml/min), and stopped the hemodialysis. Although it may not be necessary to slow the blood flow rate before discharging the chamber, we were concerned about transmembrane pressure and venous pressure elevation by pushing a portion of the blood volume from C-C, so we slowed the blood flow rate before blood was discharged from C-C. Then we put 60 ml BV into the body from the C-C. Twenty minutes after increasing the intracorporeal BV artificially, we measured the systolic BP to see if there was an increase of 20 mm Hg or more or recovery of systolic BP to greater than or equal to 110 mm Hg. In the control group, 20 ml of 10% NaCl was administered intravenously when hemodialysis collapse occurred.
Analysis of variance and paired t tests were performed for statistical evaluation. Values of p less than or equal to 0.05 were considered to be significant.
Hypotension Induction by Starting Hd
We measured the systolic BP and heart rate (HR) at the following points and evaluated the hemodynamic changes: 1) immediately before inserting the needle into the shunt, 2) immediately before C-C filling (10 minutes after connection of the circulation circuit), and 3) 10 minutes after C-C filling. There was no significant decrease in BP during these processes (Figures 2a and 2b).
Effect of the Charging Chamber on Blood Pressure Recovery from Hemodialysis Collapse
We compared the systolic BP and HR (for C-C and control) at the following points and evaluated the effect of BP recovery: 1) before the start of hemodialysis, 2) 30 minutes before hemodialysis collapse occurred, 3) When hemodialysis collapse occurred, and 4) 5,10,15 and 20 minutes after hemodialysis collapse occurred (5,10,15 and 20 minutes after blood administration from C-C), 5) immediately before the end of hemodialysis, 6) 20 minutes after the end of hemodialysis. At hemodialysis collapse, systolic BP decreased by 38.6 mm Hg (p = 0.0002) and HR increased by 12.0 bpm (p = 0.0226); however 5, 10, 15, and 20 minutes later, systolic BP recovered by 18.0, 22.1, 24.2, and 26.0 mm Hg (p = 0.0054, 0.0052, 0.0085, 0.0072), and it was possible to maintain a definite BP elevation immediately before ending hemodialysis and 20 minutes after ending hemodialysis, compared with the time of hemodialysis collapse (Figure 3 a,b,c).
Recovery Effect from Hemodialysis Collapse by Intravenous Administration of 10% NaCl
For the C-C study, systolic BP and HR at points 1–6 were compared and the effect of BP recovery was evaluated. The results were that, at hemodialysis collapse, systolic BP decreased by 40.6 mm Hg (p < 0.0001) and HR increased by 10.0 bpm (p = 0.0057); however, 5, 10, 15, and 20 minutes later, systolic BP recovered by 20.5, 24.2, 28.7, and 30.2 mm Hg (p = 0.0025, 0.0056, 0.0004, 0.0003), respectively (Figure 3c).
Comparison of the Bp Recovery Effect
Hemodialysis was performed under the condition of water deletion shown in Table 2 (by the C-C and 10% NaCl methods) and degree of BP recovery (ΔBP) was evaluated by using paired t tests. Total amount of fluid removed with the C-C and 10% NaCl methods was 2.14 (SD; 0.62) kg and 2.11 (SD; 0.62) kg, respectively. Total hemodialysis time with the C-C and 10% NaCl methods was 228.5 (SD; 39.7) minutes and 226.0 (SD; 39.3) minutes, respectively. There were no significant differences in total amount of fluid, total hemodialysis time, and BP recovery effect at 5, 10, 15, and 20 minutes (p = 0.5346, 0.8315, 0.6342, 0.4196, respectively; Figure 4).
Blood Clotting in the Chamber
Blood clotting occurred in the venous chamber in 1 of 10 patients. However, in that patient, even during usual dialysis, a small amount of blood clotted in the dialyzer. However, during the next dialysis session when the amount of heparin was increased 1.5 times, blood clots did not form in the chamber. Blood clot formation in the circuit was not observed in the other patients during usual dialysis or C-C dialysis.
Risk of Pushing a Portion of the Blood Volume Back Into the Dialyzer
At the time of discharge, there is a potentially serious risk of pushing a portion of the blood volume back into the dialyzer and not into the patient; however, there was no change in transmembrane pressure and venous pressure, so there was no machine alarm.
Influence of Increased Priming Volume
To increase intracorporeal BV during hypotension, we made it possible to change the volume in the chamber in the venous line of the extracorporeal circulation circuit. As a result, compared with the priming volume of the usual extracorporeal circulation circuit (70–170 ml), volume increased slightly to 172 ml. However, neither a significant decrease in BP nor an increase in HR at the initiation of the extracorporeal circulation was induced.
Influence of Chamber Structure Complexity
The chamber structure becomes more complex with the added ability to change the volume in the venous chamber; therefore, blood clot formation in the chamber becomes a concern. Results showed that distinguishable clot formation was not noted in C-C except for one patient who had a tendency to form blood clots in the circuit even during usual dialysis. Distinguishable clot formation was not observed by increasing the amount of anticoagulant, thus, it seemed that if clot formation in the circuit was not observed during usual dialysis, it would not be observed during dialysis using C-C.
Effect of BP Recovery
The 10% NaCl solution has hypertonic osmolality and increases effective circulating blood volume temporarily, so it has been reported that hypertonic saline is effective for hemodialysis collapse.11 This study has proven that using C-C attains almost the same effect of BP recovery as the intravenous administration of 20 ml 10% NaCl. With this method, BP recovery is possible without the need for injection of additional solutions. Therefore, it is a useful method that has the added advantage of reducing medical costs.
It is possible to reduce priming volume by reducing the volume of the arterial chamber or the inner diameter of the blood circulation circuit. With the current circuit, hypotension did not occur during blood withdrawal at the beginning of dialysis; however, the risk can be reduced further by any decrease in the priming volume.
The most complicated technique in the dialysis method using C-C is to manually withdraw any air from the venous chamber or to return blood into the body rapidly. The speed of the operation and the adjustment of the volume are dependent on the operator’s manual skill at present. The development of a device that automatically withdraws air from the chamber and administers blood volume as needed is under investigation. This blood charging and discharging is available only one time, so it is not available for patients with repeated hypotension during a single dialysis session.
Blood clot formation in the chamber should be fully considered, and it is necessary to examine the increase in anticoagulant according to the need.
Until now, infusion has been performed to increase BV for hemodialysis collapse. Our study proved that BP recovery is possible by returning blood from the chamber directly into the body using a charging chamber for hemodialysis collapse. The concept of the charging chamber is new and has an economical advantage, because dialysis can be resumed without infusion. Also, additional water deletion for the volume of infusion is not needed, so the efficiency of the dialysis session increases. If hypertonic saline is used, thirst appears frequently and angiopathic change may occur. Therefore, dialysis using C-C seems to be an effective method for treatment of hemodialysis collapse.
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