DK152966B - PROCEDURE FOR MANAGING AN EXTRACORPORAL HAEMODIALALYSIS SYSTEM AND APPARATUS FOR USE IN EXERCISING THE PROCEDURE - Google Patents

Description

in

DK 152966B

The invention relates to a method of the kind set forth in the preamble of claim 1.

Kidney disorders are a serious matter for a person's life. Many species of kidney disorders interfere with the kidney's function, so that the kidney stops removing waste and excess water from the blood. When the kidney is so severely damaged that a large part of the waste products and water is not removed from the blood, the patient's life cannot be saved unless the function of the damaged kidney is artificially exerted in some way. Many new methods have been developed to perform renal function outside the body. Yet, even with the latest known renal apparatus for out-of-body placement, the same general procedure for dialysis of the patient's blood is used as that used at a very early stage to treat renal disorders. Eg. the most commonly used method of dialysis of a patient's blood outside the body requires the surgical establishment of a subcutaneous, arterial-venous fistula. Subsequently, the subcutaneous venous system dilates secondary to increase the blood flow that is diverted from the artery to the vein through the fistula. Sufficient blood flow can then be obtained for dialysis by venipuncture with needles having large bores. Usually, two needles with an internally styled or trocar are used to perform two venous punctures on the patient so that two blood connection sites exist simultaneously in the patient. The blood may conveniently be withdrawn from one of the punctured blood vessels, passed through the hemodialysis apparatus and then inserted into the other blood vessel.

The previous practice mentioned above has been found to have serious disadvantages for both the patient, the treating physicians and the technicians. The problem is greatly exacerbated because most patients who need to have hemodialysis performed outside the body must be treated as frequently as 3-7 times a week. This means that if all venous punctures drop out successfully, a patient must have performed from 6 to 14 venous punctures or cannulas per day. week.

The duration and good function of a fistula formed by venous puncture is inversely proportional to the number of venous punctures. Tissues that are repeatedly subjected to trauma as a result of venous puncture are numerous

2 DK 152966 B

more prone to thrombophlebitis, paravascular haemorrhage, lump formation and infection. In fact, in patients who have had multiple venous punctures, it is often found that the tissue surrounding the most accessible veins forms large hematomas that render the veins indistinct and make it extremely difficult to perform lucky venous punctures due to insufficient blood flow in the veins. damaged blood vessels.

Another factor contributing to the problems is that once one lucky vein puncture is performed and blood can flow from the patient's body to an hemodialysis device, the blood volume in the patient's body is reduced, making the second vein puncture very difficult. It has been found that while most experienced physicians or nurses are able to perform the first venous puncture without much difficulty, it is often necessary to make several attempts before another venous puncture can be performed on the same patient.

In addition, the patient understandably suffers from pain and discomfort, and that the many trials that venous puncture is often needed to place the second cannula result in growing anxiety and fear both in the patient and in the treating physician or> nursing, further reducing the likelihood of a lucky venous puncture.

It has been found that the efficiency of single-fistula dialysis is remarkably improved by increasing the stroke volume f of the dialysis system, which means the blood volume flowing past a given point in the hemodialysis system system in each of the system's work cycles (for example, in the period between two consecutive successive closures of the arterial cord) or, in other words, the blood flow rate (ml / min) divided by the number of duty cycles per hour. minute for the hi-mode analysis system. Increasing the stroke volume increases the efficiency because the admixture of undialyzed blood which, by dialysis with a single fistula, is inevitably present in a "harmful space" in the system will be reduced.

Some systems have used pressure regulators or time-controlled hose clamping means to regulate blood flow out of the patient and into the dialysis apparatus and then from the dialysis apparatus back to the patient. In such systems care must be taken to ensure that blood

3 DK 152966B

the flow rate out of the patient is generally as large as the blood flow rate in the return line. When the flow rate in the arterial line (away from the patient) and the venous line (back towards the patient) is the same, the stroke volume cannot be maximized. This will be understood when considering that an increase in blood flow rate also requires a corresponding increase in the number of duty cycles per day. per minute for the dialysis system.

The object of the present invention is to allow for variations in stroke volume so that the efficiency of hemodialysis can be maximized.

This is achieved by practicing the method mentioned in the preamble as set out in claim V's characterizing part. Although the method according to the invention can be used in connection with a large number of systems or systems for use outside the body, it currently appears to be particularly advantageous for dialysis through a single venous puncture. Once the venous puncture has been performed, the blood is removed from the puncture site through the arterial branch of a two-part bloodstream at a pressure low enough to prevent collapse of the arterial branch or patient's blood vessels. The bifurcation site is located closest to the cannula connector to keep the resulting dead space as small as possible. The blood is then fed to the hemodialysis apparatus placed under pressure outside the body while the venous branch is closed. Thereafter, the venous branch of the two-part flow path is opened for a predetermined time so that the blood can again be returned to the venous puncture site. The return time in the venous branch is regulated such that the rate of return differs from the flow rate in the arterial branch. The procedure of using a single venous puncture is made possible by alternately allowing blood to flow into and out of the patient at the venous puncture site. For example, a unidirectional pulsed blood flow through the dialysis apparatus is established. know that the blood is passed from the patient at a pressure which does not cause the patient's blood vessels or arterial branch to collapse. Meanwhile, the venous branch is closed so that a pressure develops in the dialysis apparatus.

DK 152966 B * 4

For example, in the method of the invention, blood may be drawn from the patient through the arterial conduit at a flow rate that does not cause the bloodstream conduit to collapse, the venous conduit may then be closed while blood is continued to be aspirated until the venous conduit a predetermined high pressure is reached. Thereafter, the venous line is opened and, at the same time, the arterial line is closed for a predetermined time interval to pressurize the blood into the patient, ensuring that the time that the venous line is open is less than the time the arterial line is open.

The invention has also provided an apparatus of the kind set forth in the preamble of claim 4, and the apparatus is peculiar to the characterizing part of claim 4.

The apparatus may have means for pumping blood in a direction from the patient through the open arterial line at a pressure which does not cause the blood-conducting cord to collapse, means for closing the venous cord while pumping blood, which closure means comprise a first independently variable control means holding the venous conduit closed until a predetermined blood pressure is achieved in the system, means for opening the venous conduit and substantially simultaneously closing the arterial conduit, which openings having a second independent variable control means allowing the accumulated blood pressure to inject the blood into the patient for a predetermined interval of time, the length of time in which the arterial cord is closed is greater than the period in which the venous cord is closed.

In the following, the invention will be explained in more detail with reference to the drawing, which shows an embodiment of the apparatus according to the invention.

The drawing shows a hollow cannula 24 adapted to be placed in a patient's blood vessel. The cannula may be placed in the blood vessel by any suitable technique, e.g. venipuncture.

DK 152966B

The cannula 24 can be any suitable type and a suitable cannula is a "14-gauge" catheter with a length of between 25 and 50 mm. Nevertheless, one can also use a cannula or any other hollow instrument that can be effectively inserted into a vein.

In this specification, the cannula means any hollow tube that can be placed in a patient's blood vessel.

In the embodiment shown, the cannula 24 has a bifurcated connecting piece 28. The connecting piece 28 has an arterial branch and a venous branch, the arterial branch of which is conventionally connected to a rubber or plastic tube 34. The tube 34 will hereinafter be called the arterial cord 34.

The arterial conduit 34 is disposed over the end surface of a blood pump, which is generally designated 38. The blood pump 38 is conventional and usually has a rotatable shaft 40 on which is mounted a cross bar 42. The bar 42 has at its ends 44 and 46 rotatable cylinders 48 and 50 respectively.

About half of the circular path passed through the cylinders 48 and 50 is surrounded by a semicircular groove 52. The arterial conduit 34 is caused to follow the inside of the groove 52. Thus, the arterial conduit 34 will be compressed between the cylinders 48 and 50 and the groove 52 as the cylinders pass through their circular path about the axis 401 s axis. The rod 42 normally rotates about the shaft 40 in the clockwise direction, so that the compressed portion of the arterial conduit 34 is formed between the cylinder and the groove 52 at the forward end thereof, and advances along the entire interior of the groove toward the rear end thereof. As the compressed portion of the arterial conduit 34 advances along the inside of the groove 52, blood in the arterial conduit 34 will be squeezed into a dialysis apparatus which is generally designated 60. It will be seen that as the cylinder 48 reaches the posterior end 58 of the groove 52, the cylinder 50 will engage the arterial conduit 34 at the front end so that, when the pump is in operation, a constant forward pressure on the blood is exerted to cause it to move to the dialysis apparatus. 60th

Any conventional dialysis apparatus may be used in connection with the described system. Blood flows from dialysis

6 DK 152966B

connected to the venous branch of the connector 28. Preferably, in the venous branch 62 is inserted a bubble chamber 64 which prevents bubbles from passing through the cannula 24 into the blood vessel. The bubble chamber 64 may be any suitable conventional bubble chamber, e.g. that used in blood infusion devices.

A pressure conduit 66 is connected to the venous conduit, preferably at the bubble chamber 64 above the blood surface level 68. Thus, the pressure inside the bubble chamber 64 and the venous conduit 62 through the conduit 66 may be transmitted to a control device designated 70. The control device 70 contains ( a) a pressure monitoring device which may be of any suitable type, and (b) a time circuit which may also be of any suitable type.

The controller 70 has a calibrated scale 82 provided with indexes such as e.g. represents mm of mercury. An indicator 84 is controlled by the pressure in the conduit 66, which is the pressure in the venous conduit, so that the indicator 84 is raised as the pressure in the conduit 66 increases, thus indicating the pressure in mm of mercury (mm Hg). Similarly, the indicator 84 will be lowered as the pressure in line 66 decreases, thus indicating the decreasing pressure in mm of mercury. The position of a manually adjustable marking means 88 indicates a set value. For example, the marking means 88 may indicate the upper limit of blood pressure in the venous conduit 62, as will be described in more detail. ...

The value set by the marking member 88 represents a maximum pressure in the venous conduit 62, so that when this pressure is reached, a clamp 150 is activated such that the venous conduit 62 is opened and the arterial conduit 34 is closed, as will be described. in more detail below. The venous conduit 62 will again be closed after a predetermined interval of time. This time interval is determined by setting a rotary knob 86 on the controller 70. Although any suitable time interval can be used, intervals between 0.5 and 1.5 seconds have been found to be suitable for most single fistula systems. .

In the embodiment shown, terminal 150 is a double terminal. The terminal 150 has intersecting grooves 152 and 154 through which

7 DK 152966B

respectively, the venous and arterial conduits 62 and 34 are passed. The clamp 150 has a movable clamping means 156 disposed between the grooves 152 and 154 and which, if desired, can be alternately inserted into the groove 152 or 154 to close and pinch the arterial or venous conduit. The clamping means is controlled through electrical lines 160 and 162 which connect the clamp 150 to the control device 70.

First, the controller 70 is adjusted by moving the marking member 88 to a position to indicate the desired venous pressure. The arterial and venous conduit is made clear by filling the conduits with an isotonic saline solution. When a single venous puncture or cannulation is performed, the saline solution in the arterial and venous conduit is replaced by blood 34 and 62, respectively.

The pump continuously works to direct blood toward the dialysis apparatus 60. The speed of the blood pump is chosen to be the maximum rate at which the arterial line 34 or the patient's blood vessels do not collapse.

Assuming that the venous conduit 62 is closed by the clamp 150, blood is drawn from the patient's blood vessels through the cannula 24 and the arterial conduit 34 and into the dialysis apparatus 60. Continued pumping by the pump 38 causes the pressure in the venous conduit 62 rises because this conduit is closed in the trough 152. As the pressure rises, the indicator 84 will rise to the set value indicated by the marking means 88. When the set value is reached, the clamp 150 will be affected thus; the venous conduit 62 is opened and the arterial conduit 34 substantially closed simultaneously.

It is important that the arterial conduit 34 be closed for a predetermined time interval selected by the pushing of the button 86 and made just far enough to reduce the venous pressure when injecting blood into the patient through the cannula 24. It has been found that the time required to return an amount of blood to the patient through the venous line is proportional to the pressure exerted on the blood in the bubble chamber 64. Accordingly, a higher pressure setting by means of the marking means 88 will result in shorter time intervals.

8 DK 152966 B

valves for opening of the venous cord. In the illustrated embodiment of the apparatus according to the invention, it is presently preferred that the time interval in which the venous conduit is open is less than the time interval in which the venous conduit is closed. In a preferred embodiment, the opening time of the arterial duct compared to the opening time of the venous duct is advantageously kept, for example, in a ratio of 2: 1. The flow rate through the venous conduit to the patient will depend on the pressure produced in the bubble chamber 64 while the venous conduit is closed.

Although the above-described embodiment emphasizes the value of producing a greater flow rate in venous conduit 62 than in arterial conduit 34, it is sometimes desirable to maintain low pressure in dialysis apparatus 60. In this circumstance, for the flowing blood through the arterial conduit 34 becomes larger than through the venous conduit 62. This, when using a low pressure dialysis apparatus, can be easily achieved by simply tuning in to a larger time interval by means of the button 86, e.g. up to as much as several seconds allowing blood to flow back more slowly. The small pressure gradient in the venous conduit 62 resulting from the low pressure dialysis apparatus ensures that the rate at which blood flows back is less than the rate at which blood is withdrawn from the patient.

It is noted that the speed of pump 38 is regulated so that the blood is not withdrawn so rapidly from the patient that the arterial cord or the patient's vein collapses. However, a greater rate of return flow does not entail any risk of collapse of the venous line or the patient's vein, and the greater rate of return flow is advantageous to maximize system efficiency.

From the foregoing, it can be seen that improved dialysis of a patient's blood with a single venous puncture can be achieved as the stroke volume is increased by withdrawing blood from the patient at a relatively low rate and injecting the return blood at a relatively high rate. A surprising and advantageous improvement has also been noted at this plant: Blood mixing

Claims (4)

It will be appreciated that other specific embodiments of the invention may be provided without departing from the scope of the invention. The embodiments described are intended to be illustrative only and not limiting. A method of controlling an extracorporeal hemodialysis system with one arterial conduit (34) that carries blood away from a patient, a venous conduit (62) that directs blood back to the patient, a dialy interconnected between the arterial and venous conduit sator (60) for forming a closed system and with pumping means (38) arranged to pump the blood through said conduits (34, 62), the arterial conduit being alternately opened and closed, while the venous conduit is substantially simultaneously closed and opened, respectively, characterized in that the venous conduit (62) is opened and the arterial conduit (34) is substantially closed simultaneously when a predetermined blood pressure value has been obtained in the closed system on the pressure side of the pump means (38) and the duration of the venous conduit opening time and the arterial conduit closure are different from the venous conduit closure duration and the arterial conduit opening time; The method according to claim 1, characterized in that the duration of the venous conduit opening time and the arterial conduit closure time is made less than the duration of the venous conduit closure and the arterial conduction opening time. Method according to claim 1 or 2, characterized in that the duration of the venous line opening time and the arterial line closing time is controlled by an adjustable timer (86). DK 152966B Apparatus for carrying out the method according to claim 3 and having an arterial line (34) for transferring blood from a patient, a venous line (62) for returning blood to the patient, a dialyzer coupled between the arterial and the venous line. (60), pump means (38) adapted to pump blood through the patient's arterial line (34), clamping means (150) to alternately close the arterial and venous line, and control means (70) for controlling the functioning of the clamping means, characterized in that the control means (70) for controlling the clamping means (150) comprise a pressure monitoring mechanism (84) which serves to monitor the pressure in the venous conduit (62) and has means (88) for adjusting via a pressure transducer (66) of a predetermined pressure level obtainable in the venous conduit (62) and adapted to send via a feedback (162) a signal to the clamping means (150) to open the venous conduit and substantially simultaneously close the arterial conduit when the predetermined pressure level has been reached in the venous conduit (62), and the control means (70) also includes an adjustable timer (86) for setting a predetermined time interval for determining the time during which the venous conduit (62) is open and the arterial line (34) is closed, the timer (86) being arranged to send a signal to the clamping means (50) after a predetermined time interval, through a feedback (160) the venous conduit (62) and opening the arterial conduit (34).