WO2014096499A1

WO2014096499A1 - Device for inducing therapeutic hypothermia

Info

Publication number: WO2014096499A1
Application number: PCT/ES2013/070907
Authority: WO
Inventors: Juan Antonio NUÑO MORALES; Alberto GÓMEZ BAREA
Original assignee: Servicio Andaluz De Salud; Universidad De Sevilla
Priority date: 2012-12-20
Filing date: 2013-12-20
Publication date: 2014-06-26
Also published as: ES2478695B1; ES2478695A1

Abstract

The invention relates to a device for inducing therapeutic hypothermia, comprising a blood pump combined with a Peltier-type thermoelectric refrigerator that allow the temperature of a patient's blood to be modified extracorporeally. The device comprises means connected to the pump and to the refrigerator, for extracting at least part of the blood flow of the patient, passing it through said pump and the refrigerator, and sending it back to the body of the patient.

Description

DEVICE FOR INDUCING THERAPEUTIC HYPOTHERMIA

OBJECT OF THE INVENTION The invention is framed within the field of medicine, and more particularly within the field of devices used to induce hypothermia in a patient.

The object of the invention is a novel device for inducing hypothermia in a patient that involves performing an extracorporeal cooling of the patient's blood flow and the corresponding overheating.

BACKGROUND OF THE INVENTION

Induced or therapeutic hypothermia, that is, causing the reduction of the central body temperature below 35 ° C, is a therapy that is frequently used to mitigate various types of neurological lesions. Currently, its use is more frequent in patients who they remain in a coma after cardiac arrest, although it can also be used for many other indications, such as severe traumatic brain injury, stroke, myocardial infarction, and many others. The main objective is to reduce the demands of tissue oxygen, which exerts a protection of the vital organs (brain, heart, kidney), decreasing the heart rate, increasing coronary irrigation and improving myocardial perfusion, as well as decreasing inflammatory mediators that would worsen even more the forecast. The devices currently used to cause hypothermia are fundamentally of two types:

- Heat exchanger catheter This system is based on the introduction of a catheter into a large caliber vessel, such as femoral or subclavicular. Next, a low temperature fluid is passed inside said catheter, producing a heat exchange between said refrigerated fluid and the blood, without these ever getting mixed, resulting in the cooling of the blood flow. This is achieved thanks to a chamber adjacent to the catheter as a closed circuit where a flow of cold serum enters and exits. - Thermal blanket

This system is based on the use of thermal blankets cooled by means of an internal fluid circulation system connected to a cooling machine that allows to program the desired temperature of the water circuit. These thermal blankets are used to wrap the patient's chest, thus reducing the body's temperature.

Although both systems work reasonably well, they have several drawbacks. A major drawback is the large size of the equipment used in both cases, since both must include all the necessary equipment to circulate the cooling fluid according to a cooling cycle. In addition, in the case of the thermal blanket, the very nature of the system prevents its use in certain types of patients, such as burned patients. Another important drawback is the high price of both systems.

Consequently, there is still a need in this field for new improved devices that allow inducing therapeutic hypothermia in a patient in a more efficient, safe and economical way.

DESCRIPTION OF THE INVENTION

The present invention describes a device for inducing therapeutic hypothermia in a patient that solves the problems described thanks to the fact that it comprises a blood pump combined with a Peltier-type thermoelectric cooler that allows extracting out and modifying a patient's blood temperature in a controlled manner, Dynamic and programmed. That is, instead of indirectly cooling the blood of the patient, as is the case in devices currently known, the device draws blood from the patient's body, modifies its temperature using the Peltier-type refrigerator, and the reintroduces into the patient's body at a different temperature. Preferably, means connected to the refrigerator and the pump are used that allow at least part of the patient's blood flow to be extracted, passed through said refrigerator and pump, and reintroduced into the body. For example, it may be an input catheter and an output catheter connected respectively to the pump and the refrigerator, or vice versa, since in principle, it is not important if the pump is placed before or after the refrigerator according to the direction of circulation of blood flow It should also be noted that although, in general, "refrigeration" or "cooling" will be referred to herein, the hypothermia induction cycle in a patient comprises a cooling stage and subsequently a controlled reheating stage of blood temperature.

A Peltier-type refrigerator is based on the so-called Peltier-Seebeck property, which is that when an electric current is passed through two metals or semiconductors connected by two Peltier junctions, a temperature difference between these junctions is induced. In other words, the Peltier effect allows a temperature difference to be obtained from the application of an electrical voltage. Applying this effect properly, it is possible to design a refrigerator without moving parts or thermodynamic cycles, but mainly formed by metal plates that, depending on the applied voltage, are cooled to exchange heat with a fluid that is passed near its surface. Alternatively, by inverting the applied voltage it is possible to heat the plates, which allows to increase the temperature of the fluid.

A Peltier type refrigerator, therefore, is a device that serves to modify the temperature of a fluid, in this case blood, only from the application of electric current, without the need to use cooling fluids or thermodynamic cycles. This represents a great advantage in relation to the current devices where the modification of the temperature of the fluid is achieved through the exchange of heat between two fluids, which are the blood itself and a cooling fluid, since this implies the use of bulky equipment necessary for the refrigerant to perform a thermodynamic refrigeration or heating cycle. The device of the invention, on the other hand, is small in size and only requires a connection to the electricity network and optionally a battery to disconnect it from the network if necessary, which greatly facilitates its use and transport.

In addition, in the device of the invention the cooling / heating is carried out directly on the patient's blood, so that it is easy to accurately measure the temperature of the blood flow that returns to the patient to maintain a better control of its temperature bodily. This represents an important advantage, since for the application of induced hypothermia without causing damage to the patient it is necessary to maintain the patient's temperature within certain ranges, as well as limit the cooling and heating rates. Therefore, in order to adequately control the temperature at which the patient's blood cools / heats, the device of the invention preferably further comprises two inlet blood temperature sensors and two outlet blood temperature sensors connected to a control means capable of controlling the operation of the refrigerator. The control means can act at least on the voltage that reaches the Peltier refrigerator, so that its cooling / heating capacity can be increased / decreased depending on the blood temperature that is desired at any time. In principle, the control means can use any control strategy suitable for this process, although preferably it is used

a derivative integral proportional control (PID) scheme.

The device of the invention can be provided isolated or combined with another machine commonly used in the medical field. For example, one could take advantage of the blood pump that hemodialysis machines have to design a device that combines both, thus achieving a versatile device with different modes of operation, thus highlighting the versatility of the invention. BRIEF DESCRIPTION OF THE FIGURES

Fig. 1 shows a scheme of a device for inducing therapeutic hypothermia according to a preferred embodiment of the invention. Fig. 2 shows a diagram of a patient with whom the device of Fig. 1 is being used

PREFERRED EMBODIMENT OF THE INVENTION A preferred embodiment of the invention is described below with reference to the attached figures.

Fig. 1 shows a diagram of the device (1) according to the present invention where the different parts that compose it are appreciated. Specifically, the device (1) has a blood pump (2) connected to a Peltier type thermoelectric cooler (3). An input catheter (7) receives blood from the patient, for example from the subclavian or femoral, and leads in this example to the pump inlet (2), while an outlet catheter (8) conducts blood from the refrigerator outlet (3) and returns it to the patient at a modified temperature . The inlet catheter (7) has a temperature sensor (4) connected that measures the inlet temperature (Te) of the blood to the device (1) and the outlet catheter (8) has a temperature sensor (5) that measure the outlet temperature (Ts) of the blood to the device (1). Note that it would also be possible to add a redundant sensor to both the input and the output. Thus, the device (1) would have two input sensors (4) and two output sensors (5) to minimize failures due to failures. In any case, the sensors (4, 5) of the inlet (Te) and outlet (Ts) temperature are connected with a control means (6), which in turn acts according to the information received and a program desired on the refrigerator (3) and the blood pump (2). The feeding of the pump (2) and the refrigerator (3) is carried out in this example by means of a plug (9) connected to the mains. In addition, the device (1) can include batteries (not shown) for feeding the pump (2) and the refrigerator (3) that would allow it to be unplugged from the network to facilitate travel through the hospital. The device (1) of the invention is designed to control the entire induction process of therapeutic hypothermia, whereby in a first phase there is a cooling of the blood flow through the device. That is, the outlet temperature (Ts) is lower than the inlet temperature (Te). The cooling is carried out for a certain time until the desired temperature is reached, which is maintained for as long as necessary. Subsequently, once the patient's medical conditions advise to end hypothermia, slowly begin to return to the normal temperature of the patient, so in this phase the outlet temperature (Ts) is higher than the inlet temperature (Te ). This whole process is carried out under the control of the control means (6), which implements a feedback scheme of a derivative integral proportional type that allows to establish in a dynamic and controlled way the outlet temperature (Ts) of the blood flow according to the needs in every moment. To facilitate this process, the control means (6) can have programming means that allow selecting the final temperature and the cooling / heating rate of the patient's blood flow. Thus, the user only has to adjust the programming of the device (1) according to the application particular, and the controller itself (6) is responsible for managing the operation of the refrigerator (3) to follow the desired program.

Fig. 2 shows a device (1) as described during its use for the induction of therapeutic hypothermia to a patient and overheating. It is appreciated that the size of the device (1) of the invention is much smaller than that of the devices known at present, so it is easy to transport and connect, very useful since these patients usually require tests such as angiography, CT, NMR, etc. Furthermore, in relation to the above devices based on the exchange of heat with blood flow by means of a catheter inserted in a bloodstream, the device (1) of the invention has the advantage that the catheters (7, 8) of input / output are conventional catheters. On the contrary, the catheter used in said previous devices must have very special properties, since it must have a section with excellent thermal transfer properties that allow heat exchange between the cooling fluid and the blood flow. These requirements make its use very difficult, since it is essential to use very expensive catheters designed specifically for this use.

Claims

1. Device (1) for inducing therapeutic hypothermia, characterized in that it comprises a blood pump (2) combined with a Peltier-type thermoelectric cooler (3) that allows the temperature of a patient's blood to be extracorporeally modified.

2. Device (1) according to claim 1, further comprising means (7, 8) connected to the pump (2) and the refrigerator (3) that allow to extract at least part of the patient's blood flow, pass it through said pump (2) and refrigerator (3), and return it to the patient's body.

3. Device (1) according to claim 2, wherein the means (7, 8) comprise an inlet catheter (7) and an outlet catheter (8).

4. Device (1) according to any of the preceding claims, further comprising a sensor (4) of the inlet blood temperature and a sensor (5) of the outlet blood temperature that are connected to a control means ( 6) to control the operation of the refrigerator (3) in order to maintain a desired blood temperature at the outlet.

5. Device (1) according to claim 4, wherein the control means (6) comprises a derivative integral proportional control scheme.

6. Device (1) according to any of claims 4-5, wherein the control means (6) further comprises programming means that allow selecting the final temperature and the cooling / heating rate of the patient's blood flow.

7. Device (1) according to any of claims 4-6, wherein the inlet blood temperature sensor (4) and the outlet blood temperature sensor (5) are arranged respectively in the catheter (7) input and catheter (8) output device (1).

8. Device (1) according to any of the preceding claims, comprising a plug (9) for connection to the power supply network for the refrigerator (3) and the pump (2).

9. Device (1) according to any one of the preceding claims, further comprising batteries for powering the refrigerator (3) and the pump (2).

10. Device (1) according to any of the preceding claims, which is combined with a hemodialysis machine.